'75 360 Rebuild, Cam?

Have you considered a solid lifter camshaft?
On the street, with 9.5Scr,an automatic,3.55s, and mileage a consideration,
IMO
you need to keep the advertised duration as short as possible,commensurate with putting the power closer to where to are gonna be actually driving at.
400hp is nice and all, but with your gears it doesn't arrive until about 50 mph.So now a big TC will get you past the problem, but there goes the fuel-mileage.
A modest duration solid lifter cam can give you the bottom end efficiency for actually having fun without having to floor it all the time.
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I got greedy and installed a 292/292/108 and regretted it almost right away. I swapped it out for a 270/276/110 and was way happier. That 276 was a 223@050, pretty small, but dynomite fun with 3.55s