E39a Galant
 

can .HEX EVO7-8 ROMs be writen to EPROM chips and installed in a JDM e39a galant VR4 ECU?

The early Galant VR4s have a twin board ECU which is non dataloggable.
The later ones (from about 1990) are similar to the evo 1 - 3 ECUs and can be data logged.
There's always been off the shelf eproms available for those, I used to copy them 15 or so years ago.
As for copying an evo 7 or 8 rom, well most things are possible if you know what you're doing but they use a different processor. It makes more sense just to swap in the whole ECU, wiring, AFM , injectors etc, then you get OBD2 as well as a flashable ECU.