The 66/67 Chargers are my favorite muscle cars of all time, so I have really studied these two kits and have built them both.
The MPC kit is good and everything fits well however the trim, badges and name plates are VERY shallow and easy to lose under paint.
The Revell kit is nearly perfect in every way. There is some concern that the body line from the b-pillar back dips a bit, but it is very hard to detect.
Both kits are '67s, however (correct me if I'm wrong) the only exterior difference between '66 and '67 is the front top-of-fender turn indicators present on the '67. Sand them off and you have a '66. The rest is all interior differences. If the resin pieces fit the Revell kit (or can be made to), I recommend using it.
Please keep us posted on this project.