Stroke what you have; there are some great kits out there. Or, throw a new cam in it, some good heads and you will be surprised at what you get. Also need to look at what gears you have; many people build engines and are disappointed at the performance when they should have or could have just swapped in some decent gears and completely change the performance of the car. A mild motor with a set of 3.55's will get your attention. Wont be a highway/interstate driver per se, but that is something you need to factor in.
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)