Most 60/70 Mopars used a a 4x10" oval speaker up front...
EZ to make a drop-in replacement by taking (2) 3.5" speakers and mounting them on a an adapter plate made out of thin aluminum like a cookie sheet. By making template and cutting round holes for mounting the speakers and creating extended end ears for mounting to studs under the dash. Next is how to connect up depending upon what head unit U have..
1. If using an mono AM Mopar OE head unit, the (2) speakers should be wired in series for an 8 Ohm load(3.2 Ohms + 3.2 Ohms).
2. If using an aftermarket stereo head unit the (2) speakers should be wired (1) to the left front output(3.2 Ohms) and (1) to the right front output(3.2 Ohms).

Just my $0.02...