Front springs 1966 vs. 1977

[1966SWB]

Hello,
I have recently registered, but I've lurked here for a long time. I am starting to rebuild my 1966 1/2T that I've owned for 20 years. It was a long fleet, but it will now be a short fleetside.

I'm going to put in a complete front end from a '77 Chev 1/2T. I have some lowering springs that I had bought some time ago for the '66. Will they fit the '77 front end?

Additionally, is there any difference between the cross members? Should I use the '77 vs the '66?

Thanks for your help. I'll post pics as I get them organized.