I think the stock performance 318 heads with 1.88/1.60 valves and 125 cc runners is what their thinking of. Add a 2.76 gear and your flying!

my 323" 4dr 4spd pulls the same as the first 4 gears of a 90's 5spd 5.0L mustang.

My 323's pistons were .060+/- down in the hole. The Aerohead performance 130cc 318 port 1.88/1.60 heads had 72 cc chambers, and could be angle milled (with an optional reset of the piston valve reliefs) , to the low 60's. You could make 8.8-9:1 compression easily with a 318 stock bottom. Most people are going to rebuild the heads anyways. I say why not?

I have a bigblock convertible 4spd cuda, and would recomend a good old mild modern 440. they can do what ever you want, and last forever inexpensively.