Need help with front sub frame swap

I have to swap out the front sub frame on my 65 cuda. I found a 68 Valiant Signet 4 door car that has had the front suspension rebuilt and if the front frame rails are good I will pick it up. He is asking $800 and it's driveable. I think that the front sub frame should be the same length and width as my 65. If anyone can help it would be great.