I had a Supra from the same time period. I believe you have the 310HP Indmar Assault. This is indeed a Chevy 5.7L block. Your engine has a carb as opposed to FI. You may have electronic ignition so you don't have to worry about points but I'm not 100% sure. Someone else will likely give you more info.

This will likely be the manual for your motor: https://indmar.wpengine.com/wp-conte...rs-Manual-.pdf