Hi

Your question is not clear at all.

Can you elaborate more. Like lens x has canon FD mount and lens y has m42 mount and you want them both with what mount. To answer your question more info about lenses is needed like who made Sears and who made Vivitar lens.

But most likely answer is no you cannot swap parts.

For example if you are using two almost identical lenses like Canon FDn 85mm f/1.8 and Canon FDn 100mm f/2.8 there is slim chance to swap mounts as they are similar inside lens (almost identical). inner linkage levers are almost the same size but if you want to use either on Canon FDn 35mm f/2.8 your out of luck as inner construction of Canon FDn 35mm f/2.8 is totally different.

Hope this helps

Radovan