I have a lot of M42 lenses - Jupiter-9, Jupiter-37A, Tair 4S, Flektogon 2.4/35 and of course Helios 44M-4. My Helios is great but some of them are in poor condition. I always buy the old lenses from reliable sellers and so far everything is okay. To use the M42-lens with the Canon camera you will need a M42-Canon adapter.
nice collection, i was thinking about jupiter 37A but first iīd like to buy helios and/or pentacon 1.8/50. yesterday i read something about helios īmodelsī bud donīt remember it. i have one adapter allready, programable. i also have one flektogon 2.8/65 but it has bayonet, and found one flexaret, hope to try it out soon... anyways iīm gratefull for your hints and for seeing your choises in lens