Battery is shagged on the Indy and I want to replace it with an Odyssey one, does anyone happen to know which one it is?

Is it a PC625??

ta,
Rich.

Measure it and compare it to the sizes on the Odyssey website?

Got a 545 for my hayabusa if thats any help.

Even the 545 will start a small block Chevvy (Ultima fit them as standard I think) so it shouldn't have any problem with your engine.