Originally Posted by tucsonjwt (Post 4872167)

I think the original question concerned gas mileage, at least in part.
I have owned many 5.3 and 4.8 new GM trucks and SUVs. In those new vehicles, with very careful driving, I got 17 mpg city and 23 mpg highway, whether it was 4.8 or 5.3. Rear axle ratio is important -3.23 best for mpg, 3.73 worst. However, my latest new vehicle was a 2010 GMC Sierra Ext. Cab with 4.8 and 3.23, and that got 15.5 city and 19 highway. If I did more conventional (less stop and go) driving I think I would have gotten 17/23 on that vehicle also. I am very anal about keeping track of mpg, and drive like your grandma (not the one from Pasadena.)
Some practical considerations would rule out the LS swap for me. In AZ you are not allowed to swap engines according to emissions rules, even if the replacement engine produces less emissions. You must have factory original engine and all factory smog components in place. Some say they get through emissions with modified/newer engines, but I always get super inspected when I go to emissions and would never pass - plus I think there are technically fines for this kind of mod.
As stated above, mpg would not improve much for a swap, assuming you are comparing the engines in a lightweight 1/2 ton truck. Most old squares get 10-12 city, 13-15 highway - but I think you can do better with a V6 and open rear end and overdrive transmission - especially highway.
I only drive my truck about 3000 miles per year, but it is a 454/SM465 3/4 ton beast with a dump bed conversion, so it is suited for my limited purpose as is, even if it is only 8-11 mpg city - which is the only place I drive it. It sits idling at stop lights more the it drives down the road.
As most forum members posting here know, the greatest cost in owning these old squares is all of the non-drive train components - over time. All of the electrical/mechanical/interior trim parts add up over time. While this is ultimately true for any vehicle, it really makes more economic sense to buy a newer (or new) vehicle and limit your other expenses. Modern trucks with LS engines in decent shape go for $7-10K and you won't have to put much money in them if you get a good one.

Originally Posted by caja_larga (Post 5182818)

I agree with vannatta. I'm in Tucson. They don't even open my hood at emissions.
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Originally Posted by raticl511 (Post 4821640)

The LS swap into my 4X4 got put off to build my daughters 72 nova. I ended up installing a 5.3 and a 700r4 into her car first. I contacted a company called Wait4me performance for the wiring. http://www.wait4meperformance.com/.
At $360 was by far the best deal on the computer tune and harness modification I found. I sent them the computer and the stock harness and they trimmed the unneeded wires and tuned the pc to my setup, ie: cam, intake, trans ...
I sent off nearly every wire under the dash and in the engine compartment from the doner truck and when I got it back, the harness I was to use was seperated from the rest with easy to read labels. That 18 months ago and I just checked his website and it looks like his price hasn't changed. @ $360 nobody else comes close.

Originally Posted by faribran (Post 4798876)

the route i have chosen to to NOT KEEP UP WITH TOTALS...... :-)

Originally Posted by dukkie (Post 6583064)

I have both sitting in the driveway:

running/driving 72 C20
and
running driving 00 Silverado 5.3l


what would i need to buy that i do not already have in order to swap the motor trans from the 00 into the 72 ?

Originally Posted by kidd79 (Post 7224304)

Donor Truck: $1500
2009 3/4 ton 4x4 Single cab long bed 6.0 w/6l90E Trans 88,000 miles.

Motor Mounts $130
Dirty Dingo Black crinkle finish

Dakota Digital Gauges: $980
White Face w/ interface module

Total $2610. Haven't even test fired the motor in the donor truck yet. Just getting started. Will probably test fire next week sometime.

Originally Posted by MalibuSSwagon (Post 7224329)

Wow where did you find that deal? I'd love to come into a LY6 6.0L for my Oldsmobile.

Right now I'm about $100 into the 5.3L I have in my truck, after selling off and scrapping the donor truck. Still have some less popular parts left so I will likely be ahead at some point.