70s D150 frames

Anyone happen to know offhand if the regular cab long bed frame is the same configuration as a club cab short bed? (Both 2wd)

I don't believe they are the same frame, but its been a long time since I've had one of each around to look at.
The frame on the 70s Dodge trucks drops down under the cab and those rear cab mounts are added to the side of the frame, and the front two bed mounting holes are brackets also added to the sides because of fuel tank clearance.
The club cab is 18" longer then the standard cab, the the rear cab mounting mounting brackets are located in a different place, and that means the front bed mounts are in a different location as well. I also suspect the drop under the cab is slightly longer under the club cab, but Dodge did have to accommodate for the fuel tank, so the drop might not have changed much.

You didn't specify year, but: This is for 1976 model year, and I can't confirm its accuracy, but maybe you can (at least in-part).

https://www.xr793.com/wp-content/uploads/2017/01/1976-Dodge-Pickups.pdf

They're different. As noted the dropped portion is longer to accommodate the club cab.

Otoh, you should be able to use a club frame from 73 to 93 . There's some differences in cross members and steering linkage but if you have both styles on hand you should be able to mix and match.

If I remember correctly.....std cab long box wheelbase is 131" and the club cab short box is 133" wheelbase