72 Blazer in need of advice

[DW56]

All

Bought my 1972 Blazer about a year ago. First 4 wheel truck I have owned. Complete opposite of my slammed 1956 Ford F-100 for sure. Enjoyed driving the Blazer the way it is shown in the pictures, but while recovering from some minor health issues, have decided to make something of this Blazer. I occasionally will use the 4 wheel drive (NP205), but not often. More than anything, I drive back and forth from the airport in it and the usual trips to the beach. Currently has a 350 carb'd motor with the TH350 trans. Motor runs fine and sounds great, but I may rebuild the motor as a summer project. Not getting double digit highway mileage out of it for sure. On the freeway at 65 miles and hour, I am usually at 3000rpm. If I could get double digit mileage and drive on the freeway at 70MPH while at 2500RPM, I would be happy. Again, total blast to drive. Really enjoy pulling up to some idiot in a Prius and blowing exhaust on them. Have plenty of them to choose from out here in Liberalville, CA

Looking for suggestions: Am thinking if I rebuild my current motor, and then change the trans to a 700r4 will the trans fit? Anyone using a gear vendors? Or, should I just change it all out for a used LSX motor/4L80E combo? What clearance problems am I going to run into if I change to the LSX/4L80E combo (have to assume the cross member for sure will have issues, but what about the transfer case)?

I have looked for links to my questions, but dont find the exact answers. I am sure they are here and that I am just missing them.

Thoughts? Suggestions?

Thanks
Dana

[DW56]

picture

[DustinU]

Guessing here but looks like a 4" lift and 33" tires? What size carb?
Do you know what gears you have? I have the same set up as you (lift, tires, motor/trans) and got 13 mpg with the old tired 350 (wasn't stop and go on the 5/405 freeway either). I haven't had a chance to check the new motor, I am running 3.73 gears. If I recall correctly, you will need to also install some 4.11 or 4.56 gears with the overdrive.

[OLD K5]

I think with 3:73 gears and overdrive will be perfect. Probably around 2200-2400 rpm on the freewayat 70mph.

[SamMargritz00]

you could always put a 5.3/4l60e in it. mine does 65mph @ 1700 rpm. gets pretty good mpg. haven't driven it enough to calculate economy. and you can get a resonable amount of power of those little engines. i love it.

[DustinU]

Originally Posted by OLD K5

I think with 3:73 gears and overdrive will be perfect. Probably around 2200-2400 rpm on the freewayat 70mph.

Again, I don't have this setup but check out this link for approximates:

http://www.ringpinion.com/Calculators/Calc_RPM.aspx

The 700r4 is .7 in OD, with 3.73 and 33" tires at 70mph you would be turning 1861 RPM. If it is a newer trans or added lockup it should be fine I would think.
On the other had 4.56 gears with this setup would have much more get up and go and turning 2200-2300 rpm at 70 mph.
Just my thoughts, I am by no means an expert.