Thanks for the feedback guys!
Yes, I’m planning on building a 289 Usrrc ffr mk4 an am trying to decide that key component, wheel size as so much depends on this.
I will not be racing but could see some auto cross and track days when life allows down the road. I definitely enjoy spirited driving, have been driving mustangs as daily drivers for 30 years. The latest is a 14gt, just a phenomenal car!
What I have to determine is how much rolling art I have to sacrifice to get a performance that is equal to or better than the 14 GT.
I would like to build a replica of csx 2000, but realize I will have to compromise on looks to meet performance and drivability goals.
I would really like to stay with 15”, willing to give up the fia knock offs and run 15” hilabrands to get the irs.
Hp goals would be similar power to weight ratio to the 14gt so 350 flywheel. Would enjoy a period engine compartment. Probably roller 302, heads, cam, Holley snipper hiding under the chrome round air cleaner. Not ready to do floor mounted pedals and fiberglass foot boxes at this time due to lack of free time.

If I should go 17’s I would probably us an f150 coyote and get to use the free brakes from the salvage yard 2015 irs.