-16 will be fine, i ran a late model with the tank in the back and that is what was used. you can use this hard line for the scavenge and supply lines and do away with the traditional cooler in front of the radiator.
https://lefthanderchassis.com/v2a/vi...dgroup=2511674
if you use soft line that will work also, will not collapse. aeroquip starlite is some pretty nice stuff and it looks like speedway has it on sale right now. still kind of expensive but i couldn't find the guy i used to buy it from, must be out of business.
Aeroquip Starlite Hose, -16 AN - Speedway Motors, America's Oldest Speed Shop
on second thought i am pretty sure it was -16 line that was used front to back, could have been -20, has been while and it was pretty big stuff. but we did run the hard line on the return and supply.