My choice tool is a ratchet spanner with a wobble head . . . easy
Well still a right pain to do but possible.
You can use S13 ones and swap the engine mount bracket over to S13 ones. Or make simple adaptor plates that pick up on the S12 engine mount brackets and the S13 engine mounts. If you can drill holes in a plate you can do it.
You can also use universal bobbin ones aswell if you want to do it on the cheap.