will a 14x7 with a 3 3/4 back spacing, and a 15x7 4inch back spacing work good on my 72?

Depends on how far you want the rim sitting inside the wheel well. I have 15 x 7's on the front w/ 4.5 bs and 15 x 8's on the back w/ 4.5 bs and they fit perfectly. So, your combo should work ok.
Nice looking car by the way. graemlins/thumbsup.gif