Motor mount help-71' Sierra 2500

[ItzhakRoberto]

I have looked through and used the search option but i mostly find threads regarding the 72 mounts as they are different ( i didn't know but i do now)
This website has been real helpful but now i need some advice or a push in the right direction. I need new motor mounts and all the things i've seen online differ a whole lot in price....i've seen some on rock auto for like $8 a pair but i've seen stuff on ebay or another website Manes trucks for about 60 or 70 a piece.....i have a 402. Where can i buy motor mounts that i know will work for my truck? a bunch of places say theirs are compatible yet....all those mounts look different .....thanks fellas..