Glad to here you're considering an inline. DARE TO BE DIFFERENT
. We, my son and I, did and we're still happy with the choice. I have no experience with a 292, but I don't think you'll find anyone that will give you a sound reason to not use a 292. The 292 is harder, but not impossible, to find and a little bit more expensive to build. We had the original, numbers matching, stock 250 in a 67 C20 that we bought so we stuck with it. The truck is a daily driver 365 days a year in upstate NY (yeah......salt, salt brine and liquid calcium.) We took a stock, 1 barrel, 145 hp 250 and made a 235 hp hopped up 250. The mods are modestly priced and worth it; basically zero decked, mild 252 cam, lumps, bigger valves, Tom Langden cast headers with dual cherry bombs, Offy intake, 390 Holley and junkyard HEI. GREAT fun. It makes ALOT of noise and turns heads. Everyone in town knows the truck (just from the sound!)
FYI - we put in a T5 and it made a night an day difference and best of all it cost $250 ($100 used T5, $65 basic kit and $85 '85 Astro van low budget clutch that bolted onto the stock flywheel.)
Hop over to inliners.org and those guys are great - they will provide 10 times more input than I can.
X2 on Bogie's recommendation of grabbing the Inline power manual by Leo Santucci - it was our bible.
If you want to see what a 292 can do, then do a search on Cotton Perry and you'll see what can be done with a 292 (and that was back in the '70's!)
But basically, if you're not concerned with 60 ft and 1/4 mile times, STICK WITH THE SIX
I tried to post a pic unsuccessfully