D'OH! I missed the whole question lol.
Yes, prettymuch any injector will fit. The E30 M42 used standard size injectors. The E36 m42 used special shorter ones that need little adapters to use other units.
Anyway, if you ran the Mustang 19.1# ones it would end up being 22.9# on our fuel system. The ECU could adjust to this. The M42 runs a little lean at full-throttle and higher RPM's. Wanna take one for the team and try this out lol? Be SURE to unplug your battery before doing this...both to avoid sparks when working with the fuel system and to reset the ECU. Usually you can get away with all sorts of stuff by resetting it!
There are 2 types of Mustang units...some with 1 pintle, and some with 4 micro-pintles. The 4-pintle ones are more desirable due to their supposed better atomization. Anyway, good luck!