58 Chevy truck with a 2017 mustang IRS rear end
The trucks going to run a 6.0 ls engine and custom chassis.
ok, let me get this straight:
you wanna put a different rear suspension under it, will run a custom chassis and obviously a different type of front suspension.
you want to go around corners fast but won't be racing against anyone but yourself really, for fun.
please explain what you mean by a custom chassis. if you mean you will cut the old frame behind the cab to accommodate a different unit from a different car, then cut the old frame ahead of the cab and install some sort of IFS up front, then in that case your "custom chassis" idea is really only going to be using that center section of frame to mount the cab and there will be multiple areas in which to mess up the chassis being square and true plus a lot of welding to the frame length just to install different suspension parts on each end. you will likely be removing cross members along the way even in the middle section in order to make drivelines work since I assume you want the old truck to sit as low as a newer style "donor" muscle car. maybe an idea to consider would be to start with deciding what you want and then start from scratch building a new frame to accommodate the suspension choices you have made. really, these frames are pretty flat, front to rear, with a small kick up over the rear axle and some tapering out front. you could fab your own frame using the GM dimensions from the assembly manual drawings. then you could use box tubing, to eliminate the need to spend time and money boxing the old frame, all the steel would be new and not prestressed from years of work, no unrequired frame holes to spend time welding closed, etc etc. it may be worth your time to research a few manufacturers and see how they have built their frames and then come up with a plan for yours.
I did a quick google and found this
Crown Vic front suspension track width is about 67″ wide as measured from hub / hub. this is not wheel to wheel, hub to hub.
not sure if these guys are still around but they make a narrow crown vic cross member
https://team321.com/slider/narrow-cr...t-crossmember/
they also use a ford rear IFS and have the install do it yourself on a 50's era ford here
https://team321.com/truckirs-installation-page/
these guys use corvette underpinnings. they use laser cut frame parts that are welded together on a frame bench to form the channel. nice stuff as far as I have seen in person.
https://www.canadianhotrodsinc.com/frames-chassis/
https://totalcostinvolved.com/produc...-rear-chassis/
https://artmorrison.com/products/gt-...55-59chevtruck
https://www.scottshotrods.com/1955-5...truck-chassis/
https://www.fatmanfab.com/product/19...-truck-chassis
https://roadstershop.com/product/ful...truck-chassis/
https://www.schwartzperformance.com/...truck-chassis/
https://www.gsimfab.com/1955-1959-ch...4286_8863.html
more corvette stuff
https://www.progressiveautomotive.co...short-bed.html
https://www.peteandjakes.com/new-195...truck-chassis/
https://nolimit.net/
https://pbfab.com/
lots of parts available here
https://welderseries.com/?_vsrefdom=...kaAv2iEALw_wcB
you maybe want to download a copy of this for future reference
https://www.trifive.com/d1/55-59Assy.pdf
this site gives gm drawings of newer trucks in case you want to see track widths etc
https://www.gmupfitter.com/pages/body-builder-manuals
here is a link to a thread on here that uses a crown vic on an AD truck. a few challenges including width, which was overcome by narrowing the cross member. really do some research on IFS geometry before you pull the trigger on anything
http://67-72chevytrucks.com/vboard/s...ight=crown+vic
then there is the jag front and rear suspensions that have been used in trucks since they are narrower. here is what they look like, or google it if it interests you
https://www.kwecars.com/jaguar-upgra...grade-renewal/
https://www.hotrod.com/articles/inde...nt-suspension/
here is a site that will give wheel offset comparisons and how that will affect scrub angles etc
https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm
https://www.racingaspirations.com/scrub-radius/
https://www.car-engineer.com/suspens...icle-behavior/
these guys cover a lot of the suspension theory as well. they have different tabs you can click on. really consider your wants/needs and compare with different set ups before pulling the trigger on something. that will give you the best results
https://suspensionsecrets.co.uk/anti...lift-geometry/
that should give you some ideas to look at. think about/research what you want/need for frame rigidity for the purpose you want and how that will affect the day to day ride. personally I am not partial to a hard ride every day just to go cornering once in awhile. a harsh ride tends to make you clean, polish and tinker more than drive because it is simply not comfy. lots of potential riders will also find an excuse not to be available for road trips as well. to each their own though.
how much suspension travel you want/need, what you want/need for brake rotor diameter and cooling as this will affect wheel choices, what you want/need for tire choices as this will affect the frame width at the rear. where you want/need your brake booster to mount and will it be vacuum or hydraulic. where will you place the fuel tank as this heavy item can affect the front to rear bias. if thinking of short control arms due to a wide original track width from a donor also think of how that affects suspension travel and handling etc. even a simple thing like a tire size change without considering the geometry changes that come with can really change how the vehicle handles on a track/handling scenario.