New heads

At the best, with an Ica of 62*, the pressure will come in around 150/155psi; at the BEST! More likely is 140ish
Without the pressure, the bottom end will go soft, forcing you to increase the stall and the rear gear, in that order.
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Why use 62* a comp cam xe275h is a 63* there's a lot more reasonable cams then that for a 318. Like xe250h, 51* or xe256h 54* are a more reasonable choices even the xe262h 57*, xe268h 60* are less then your eg..

I imagine you could fine similar cams to xe250h or xe256h on 108-107 for even closer lvc to the stock 48* and or change the install angle.

How much do you think you can get away with changing the lvc, how many degrees from stock 48*?

Eg. Like comps xe250h it's got to worth going 51* to gain 30-40hp.