Look for a date code near the starter on the engine block..429s were made from 68-73 IIRC..
I think they made 429 for commercial trucks thu the 90's- but they were all like a D7 or D9 casting, think they had iron front covers and those funky center dump manifolds same as the 370s. Ive often wondered if any of the commercial 370/429s had steel cranks...they were so massive, I doubt it- but still, a lot of big trucks got some super heavy stuff.
on the old ones I think the only way to tell 429 or 460 is by the stroke- both came out in 68, the 460 was put in passenger cars a lot longer than the 429- once the compression went away after 71 even the 460 was struggling to get over 200 hp...I think the 429 crank has a 'u' cast on the nose or something like that- likely would be hard to see. if you can measure the stroke, the 429 was 3.59, the 460 3.85
a little trivia that I always still kinda wonder about...there were only 2 engines over 400 cubes with rod:stroke ratios over 1.8:1 the 426 and the 429, and both were pretty sucessful, and I think this had a LOT to do with it.
short rods can generate crazy torque but also add massive drag, these 7 liter screamers though still put out pretty healthy numbers...think mine was rated 480 ft/lb at 2300 and 360(seems low?) hp at 4500 or something like that.
the cop/cj 429s also had wristpins offset to straighten the rod on the power stroke- common now I guess, but was kinda unusual back then. I had a old (early 80's) magazine that Jon Kaase built up a budget 429, if I recall right, he said the stock nodular crank/2 bolt bottom end would run 8k all day long- but he cut the mains to BBC size to reduce the bearing speeds. think these engins had 3" mains- I know that crank is a heavy SOB
everyone has their favorites, but to me the early 429 is 'it'...yeah its way heavy at over 650#, but still- its like a scaled up cleveland with better oiling