Unusual frame question

[jfnar]

I have a '77 swb stepside that is mechanically sound and the bed is very good but the cab is a rust bucket. How difficult would it be to put a '67-72 cab and front clip on the frame? I know the bed would not be the same as '67 but I think it would be close enough after it's all painted the same color. Just wondering if it's feasible. I more familiar with the '55-59 models so I'd appreciate any insight from you 67-72 guys. Thanks.