Frame rail options

Hey guys first post been a long time reader, and you guys always seem to have the answers lol,

I have a 1972 Dart that has been my baby sense high school but the front subframe has a spot about 12-14" rusted out on each frame rail between the k member and torsion bar brace. Rest of the frame rail seems to be solid still.

My question is what are my options? Should i cut and paste steel in the rusted sections, saftey cap the frame rails, or iv been looking at Auto Welds "long" front frame rail kit as well. Plz np start with a different car i understand attachment can make things cost 10xs more but it was my first car and worth the cost to build it.

I plan to make decent power (500-600) out of a stroker 440 in the next couple of years but have to make sure the unibody can handle it before i drop the money on the engine build and rest of the car. Thanks!!

Pic of my car for attention lol

Dart snow.jpg