Clearance issues 400 small block and 700r4 transmission

[rayray767]

Front driveshaft is almost butting up next to my transmission pan you can barely get a fishing string between them but it does turn freely. I tried reversing the driveshaft it doesn't bolt up right. I was told I could change out the yolks but the front and rear don't interchange. I had bought a new aluminum transmission pan it's even thicker and won't work at all. Any ideas I'm frustrated.