273 heads on a (1977) 318 block

Hi! I just bought a 318 block of 1977. I want to put on my 273 heads (1964) on it. I know we will have to adjust the bolts because of the different angle.
I just wondered if i can use the regular (flat) pistons of the 318 or can i expect to get problems with the valve clearance?

Wishing you a very good new year!

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