273 302 318 340 build

I see two stands now!
And looks like new pistons.
Ima guessing you're going 318 then?

.150 in the hole is a lot, too much for a 270* cam, if I'm reading that right. Guys are on here often enough complaining about the soggy bottom ends of their teeners with 268* cams. That .150 is 30cc on a 3.94 bore. You can't make that up somewhere else. So I hope those pistons come in closer to the top; a lot closer.
A 270 cam wants about 9.8 compression ratio. for a total chamber volume of 75ishcc; you just can't afford to gain 30cc like that. You more or less need a zero deck to get close to that 75cc, in order to enjoy that 270* cam with a reasonable powertrain behind it, like a 904 and 3.23s minimum
Of course with 4.10s and a 2800, you can drive around the soggy bottom end, but the 270 won't pull very hard in a 7.4Scr engine.There's just no cylinder pressure.
Ima lil worried for you.....