Frame Tabs & Body Mounts ????

[richcz28]

I have a 1977 gmc C15 pickup long bed regular cab 2wd that I am currently restoring. I have this truck completely torn down to the frame rails currently. Some of the tabs on the frame where the body mounts to the frame are rotted. My frame is rot free. I am looking to replace these tabs as they are just riveted on. I have searched for these tabs at reproduction shops like LMC truck. I have only found tabs for the updated frame as can be seen on page 35 of the LMC truck online catalog. I beleive the years are 81-89 or something like that. So my questions are....

Can I use these LMC reproduction frame tabs? (I have read they work with the newer body mounts.)

Are there frame tabs available for a 77 someplace else in reproduction?

Thanks.