Is there more room on the drivers side then passenger side? (seat install)

[BillGrissom]

Now does anyone know how to fill in the old holes?

I wouldn't consider welding shut the old holes. Just find a plastic body plug, or cover w/ butyl rubber. The factory pan has large drain holes (~2"D). I see no structural issues from a few extra holes. A totally rotted out floor board might make a slight difference, but you would probably need big sections of the main floor pan missing to have an effect.

 

[green1]

Every mopar I have dealt with (many); drive train offset 1 7/8", to clear the steering box.