650sx to ‘86 JS550 Hull

Just picked up a 86 JS550 Hull and a 650sx engine I’m putting in It. I’m sure multiple people have done this but for the stock 650 exhaust do I need a 650 fuel tank or 500 for figment or does it matter? also what are some other things off the top of everyones head I will need. Any help is appreciated buying the parts tomorrow so hoping to get some answers by today. Thank you guys, also any pictures of this swap would be appreciated.