g741.org

If so, I'd love to hear the details

That would be a beast; I'm not aware of anyone who's done this swap.
Gary

I've had a 375hp 396 big block Chevy in mine since about 1971 or 72, replacing the anemic Dodge 318 I installed in the mid 60s. No complaints; the 396 was a screamer, but it's time for a redo, and I'd like more low end torque. The 454 or 502 would be a bolt in swap, and I no longer need the high rpm capability of the 396.

The good news, is that a 454 is dimensionally, nearly identical to a 396...they are both big blocks with the same mount locations and trans bolt patterns. 454 is a bolt in.
Only consideration is the accessories in front.
I think the 454 accessorie package is wider than a 396...but not sure.
If you have the coin, consider swapping out the pulleys, for a serpentine package...they tend to be more compact.

" think the 454 accessorie package is wider than a 396...but not sure".

In standard configuration it is, but you can set that up however you wish.
I'd just use the same narrow setup that I put in the truck fifty years ago (I figure I'll indeed need a new harmonic balancer though...).

I'm leaning toward the 502, but I don't remember off the top of my head if they are internally balanced. I need to stick with the flywheel and large clutch that I've been using.

Edit - I checked. Both the 454 and the 502 are externally balanced (396 is internal) so I will have to modify my extra flywheel.
BTW, the truck can handle the output from these engines without difficulty. You just have to apply throttle somewhat gradually and avoid popping the clutch.

To answer my own question, there is at least one 454 and one 500 Caddy already in M37s.

I'm drifting the thread a bit.
Am considering a completely reversible installation of a Dodge 360 magnum engine in the 708.
It will require installing the long civilian pilot shaft and pilot shaft housing in the transmission, but that is reversible too.

Any thoughts?