I don’t have any first hand info on V8 swaps in the TD replicas, but
I’ll throw in my two cents worth on engine swaps in general.
Measurement of physical sizes should be easy to obtain on the web. The
radiator size for a V8 isn’t the problem it used to be since you can
get very efficient 4 row and electric fans that can cool a V8. Steering
columns can be moved, exhaust can be custom made, and motor mounts can
be fabricated. So, in short, you could put in any engine that
physically fits. (Imagine a Flathead Ford in one.).
Physical size aside, is the frame on your TD strong enough?
Is the drive train strong enough? Mine isn’t. Borrowing from some
friends experiences, it’s real easy to mismatch components and end
chasing your tail trying to get things to keep from breaking.
Again, just my 2 cents, it’s not something I think I would do. If you decide to do a V8, have fun and please post some pictures.