You should be able to get pins in oversize (maybe MOPAR HEMI cut to length), or just get the rods re-bushed & re-sized.

You need to have the block square-decked to .000" to .002" or so.

Using the offset dowells & '70 & up heads are worth a ton more HP, so good going there. You can "open chamber" those heads to flow better & reduce 12~1 compression (advertised CR w/51cc chambers) pistons down to 9.5 to 10~1 or so.

Then, you need to know how many CCs your head's combustion chamber holds, in order to calc the CR.

THEN you can consider which pistons to buy.