I have a 2000 Escalade 5.7Vortec w typical spun bearing issue. Inherited a 400 Cid chevy race motor out of a drag boat w sig erson heads,cam, roller valve train, unknown internals, torker2 intake and a 1968 302 z28 motor w performer intake. I'm disabled and broke and just want a daily driver and want to swap one of the motors to get me around. I have an hei distributor, wires too. I was going to use the performer intake and pickup a new edelbrock carb for intake. Last 400 I had was ridiculous at like 8mpg so probably going with 302 and put a matching performer cam or some kinda rv low torque towing cam in it. Motor will run on its own but how will this effect the transmission operation and shift points? Will I need some kind of outside signal box for the transmission to work properly and what about the engine ecm computers functioning now effecting other systems, sensors, Guage etc. What about just using my 302 or 400 blocks with the existing vortec heads and crap spider injection intake manifold and throttle body.? Might have to rebuild what i have or fond another wrecked gm truck or suv with a 5.7 vortec and pull n swap, but refresh oil pump, gaskets, etc. What cam suggestion too for a vortec 5.7 for towing power amd fuel mileage?I just want a normal driving reliable vehicle with good gas mileage.im 60 not 16. Any suggestions would be helpful.