Use the 292, but do not try to get by with a half-donkeyed buildup. Go ahead with a full overhaul. The cam sounds good, slightly above stock, but not so radical as to be a pain on the street. There's no need for radical cylinder head modifications- - - -the 292 has all the torque you'll ever need without getting crazy with modifications.
A single (small) 4-barrel is a better choice than any multi-carb setup unless you're a masochist who likes tinkering with carburetors more than spending your time driving. RUN- - -do not walk away fronm the 3-carb setup! If you just gotta have dual exhausts, use the cast iron headers. My personal choice would be the big-pipe single exhaust from a 292 in a medium-duty truck. Splitting the tailpipe behind the muffler will make the majority of people think you've got dual exhausts, and the performance on the street will be exactly the same as the header/twin muffler/dual pipe setup for a LOT less cost. Most of that junk is eye candy to impress the people who don't know any better.
Your HEI ignition should be a drop-in swap into the 292. Be sure to run a heavy-gauge wire all the way from the ignition switch to the distributor, about a #10 size. The 72 truck will have a nickel/chrome resistance wire supplying the coil, which drops the voltage down to about 9V during normal running. No good for HEI!
Jerry
