Yeah, if you are buying new parts or non-core parts, don't just toss the old ones. At least keep them around in case someone needs to fix a cracked case or gear to rebuild theirs. I've also given cores to people to return when they buy something and they don't have a core to return, like when you change out a factory Denso 40A alternator for a GM CS105. A guy might want to keep his still good factory alternator as backup or in case he sells the truck, so you just shove whatever core you got sitting around in the box and most of the time the counter guy couldn't care less if it's not exactly the same thing.
'91 Pickup - Imelda / '08 Tacoma TRD - Donna
'09 Kawasaki KLR650
'98 Rhygin Juke SS / '12 Gunnar Rockhound 29 / '16 REEB Dikyelous
"Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty. Nobody is able to achieve this completely, but the striving for such achievement is in itself a part of the liberation and a foundation for inner security. " --Albert Einstein