May be a little out of the ordinary, but my favorite rwd truck engine is the 455 Oldsmobile. Full dressed minus flywheel stock they weighed 620 lbs, add a cam, headers, intake, carb and updated HEI and your looking at a healthy 400+ hp and well over 500 ft/lbs of torque, all under 4500 rpm. You do need to do some oil passage work since stock was very poor on oil return and it's cheaper to stick with an automatic (preferably TH400) instead of machine work on crank for 4 speed. I find them in the wrecking yards still, strip them down, do the machine work, upgrade to a flat top piston and maybe a good 850 cfm carb, and if did most everything myself was usually able to stay within the $1500 mark as long as I picked up some used stuff like top end on ebay or craigslist. Guaranteed to be a tire shredding monster!