I would have to run the supercessions to be sure, the part #'s in the book are different. The 70 book has options like A/C as well.

I would say though that if the 68 Coronet frame is from an R/T, Superbee or other car with the round rallye guage package, and the 70 is also (with no A/C) it is quite likely to work.

If you are trying to change from square gauge to round---no.