When it comes to important seals, the rear main seal is at the top of the list. This is the OE updated, double lip design silcone rear main seal we use on every engine we build. We use OE seals for a reason, you should to. Do you really want to pull your transmission again just to replace a seal you saved $6.00 on by buying an aftermarket? Didn't think so.
We only use OE seals for our builds here at the shop. The front seal is designed a bit narrower than aftermarket seals so you can move it slightly rearward in the oil pump to avoid the groove in your front pulley.