remapping software (for mac)
KeyRemap4Macbook - this is the one i'd suggest
DoubleCommand
Karabiner
ControllerMate - is also capable but a little much just to swap a couple keys.
or look for other key remapping software
there is also hasu's wonderful converters. full keyboard remapping for all sorts of protocols even a usb-to-usb adapter
as far as a different keyboard... first figure out what switches you like and don't like. you can use just about any keyboard with your mac. the os supports swapping the modifiers which is one of the main differences (other than the numberpad) plus, if you don't like the mac style numberpad, i'd go with a standard PC keyboard/layout.
going off of this being buckling spring.... you like tactile & clicky and don't mind some noise...
- what about a PC layout unicomp keyboard - would have the 2u + on the numberpad like you are looking for (or older IBM model M's with a converter or replacement controller if needed)
- what about clicky alps
- what about some of the kalith box switches with the click bar (cherry MX compatible)
what about a vintage board & swapping switches if they are not what you want?
- apple extended keyboard I or AEKII (alps - would probably have to undampen & clickmod the AEKII to get closer to your liking)
- dell at101w (alps)
- McAlly MK96 - white clicky alps just a compact layout
- best you're going to get in a vintage MX board would be blue (clicky) or clear (tactile) ....going with that you like buckling springs.
watch some of
Thomas's videos & buy some switches to try