I usually buy the biggest trans cooler I can. On my 88 run a 160 thermostat, think the Performer has a 180, it will stay in. I think a 180 is a good compromise and some leeway if problems occur. With no fans and the small grill openings my 88 hits 195 and beyond. With the larger grill and no A/C condensor in the way, his Olds 350 should do fine.