Oil pan gasket issue (1975 Corvette)

Hey everyone, I decided to replace the rear main seal on my 1975 Corvette. Everything was going pretty good, I'm almost done with everything I just need to install the oil pan along with the new gasket. The only issue is the Fel-Pro one piece gasket I'm using isn't fitting properly onto my OEM oil pan (as seen in the pictures posted below) and there is a pretty decently sized gap at the front of the oil pan. This is with the OS34510T Fel-Pro gasket which is supposed to be the thick gasket. I also tried using the thin Fel-Pro gasket and had no luck with that either. I even tried this with a different oil pan because I had an extra one laying around and I didn't have any luck that that either. I'm not sure if I have a faulty gasket or if I somehow have the wrong one? But I don't think I have the wrong gasket because everywhere I have looked online says that this is the gasket I'm supposed to be using. Has anyone ran into a similar problem like this or have any tips they could share with me so I can somehow solve this problem? Any help would be greatly appreciated.