I've just picked up a '77 Biarritz in beautiful shape. The 425 still feels pretty strong and runs great... I'd just like a little more!

Everything about the car is original and excellent. With that in mind, I plan to crate and store the 425 just in case I want to return it to a 'numbers match' car.

I've kinda developed a 'go big or go home' attitude and as a result, I'd like to put a 500 in it.

Are there any tricks or hooks that I should be aware of?

Is there any particular 500 that would be more suitable?

I'm guessing that a 500 from a '76 would most likely be the least hassle but not sure if I can find one?

Any and all suggestions are welcome.

The 500 and 425 are basically the same size.
Swapping the 500 in should cause very few problems....especially if you get the 500 from another Eldo.

lux hauler is right, it should be pretty simple. The 425 and 500 blocks are the same size, as is a 472. You should check out the following 2 pages:

http://members.tripod.com/~CadillacMan/79cadpage.html

http://www.mindspring.com/~dburden/engine_swap.html

If you start looking for a 500, know that they were used in 70-76 in FWD (I think) Eldorados, and I'm sure they were used in all other (RWD) models in 75 and 76. An all stock 76 500cid has been dynoed at 300hp and over 500ft.lbs. torque. So you'll probably be happy. There are also performance parts available from 2 major suppliers:

MTS - http://www.500cid.com/

Cad Company/Flashcraft/Cadillac motorsports division - http://cad500parts.com/