So I dropped a 292 in my '38. I have not heard of head issues. Do they warp if you wink at them? From my understanding its a very reliable engine with great low end.
p.s. what a GREAT looking truck with a cool set up.

I was JUST like you. They wanted me to change uot the frame.. NO WAY. Your rear will get you to safe and reasonable speeds, A PLUS!

I Kept it as original as I could .. on the drivetrain.. I fought that.. but the 45mph limit stopped me.. and the widowmaker rims. :/ Why?
1. Rims/Tires: The cost of the bias ply .. okay fine.. but the rims *could* kill someone.. AND the bias ply wears out fast and tram-lines.. I went solid rims as close as original as I could get.
2. 45mph: I want to be able to DRIVE this truck for trips, and needed at least 55mph (and probably max). After gaining knowledge from these swell folks:
The cost to maintain or potentially redo the babbit bearing 235, max safe speed and rim and tire debacle .. and 6.xx rear I ended up changing out the drive-shaft, rear and trans . and engine. So I went 292ci (largest chevy inline - HAD TO STAY INLINE MAN!

) carter 400 4bbl for coolness and efficiency, nv4500 5 speed and dana 60 rear

- BETTER mpg combo(why not!?)
- BETTER power (why not?)
- LOOKS more original and stays with theme of inline 6..