After I get the retainer fitting correctly and I KNOW that seal is straight, THEN I will mark retainer relative to block. I put a dab of RTV on sealing surface and fills side grooves with RTV and install retainer. I don't use the side seals, because retainer needs to be loose to get those in and then you tighten retainer. To me, that ruins all your fitting to assure everything is straight, so I don't use them. Again, this is just what works for ME........your mileage may vary........LOL!!!!

Dave, while the billet retainer is a nice piece, just it being nice does NOT mean when it is bolted down that the seal is straight. It still needs to be fit like a stock one. The groove and the bolt holes can vary from block to block. These items are machined into the cast block. So dull tooling, improper setup, whatever, these tolerances can vary, yet all billet retainers are all CNC machined and SHOULD be exactly alike. NOT the case with every block

I have seen blocks that the groove is crooked, the bolt holes were crooked or even blocks that the rear opening was not the same side to side.