I have a nice 1972 monte carlo frame, and was wandering if the rear part of frame is the same as a 1968 -1972 chevelle. About from the firewall area weld back. I have the front that can be welded on, but don't want to ruin one if it won't work. Any input will be appreciated. Thanks

Find a frame demension sheet. I got mine off e-bay. As longa as they are both 2-door cars the frames should be the same. Monte Carlos were chevelles with different clothes on. There is a lot of stuff that interchanges. When you get your frame demension sheet measure everthing to meake sure it's with in spec. No since in using a tristed or tweeked frame with out fixing it.

I beleive the Monte frame is the same as a 4 door chevelle. The front is identical to the chevelles no need to cut it off to weld the chevelle front on.

The 70-72 Monte Carlo Frame has a 4" longer wheelbase. I believe the difference is between the doors and front wheels.

yup- it was extended between the firewall and front suspension. look at the engine placement in a Monte Carlo compared to a Chevelles of the same year some time- the harmonic balancer on a small block car is just about right over the front crossmember. this is why Chevelle headers for a big block won't fit a Monte Carlo- the suspension mounting points get in the way.
but i think they frames are the same from the firewall back- except i think they are fully boxed and might have the same rear frame horns as an El Camino.