You have to pull a 601/2/3 cam at #1 TDC otherwise you risk damaging the cam. I suppose from that point you can rotate the engine to 15*ATDC but it'll be a bear to work on the pistons without turning the crank. You might face a lot more work than if you just retime the IP when the engine's back together. No need to loosen the IP from the block, though.

Sixto
87 300D