Hmmm...
I'd have to sit down and figure out the OE* logic for activating it at the right time... Here's the memory map from the astrocde.c file in MAME:
ROM_START( gorf )
ROM_REGION( 0x10000, "maincpu", 0 )
ROM_LOAD( "gorf-a.bin", 0x0000, 0x1000, CRC(5b348321) SHA1(76e2e3ad1a66755f1a369167fdb157690fd44a52) )
ROM_LOAD( "gorf-b.bin", 0x1000, 0x1000, CRC(62d6de77) SHA1(2601faf12d0ab4972c5535ffd722b03ecd8c097c) )
ROM_LOAD( "gorf-c.bin", 0x2000, 0x1000, CRC(1d3bc9c9) SHA1(0b363a71d7585a4828e08668ebb2999c55e02721) )
ROM_LOAD( "gorf-d.bin", 0x3000, 0x1000, CRC(70046e56) SHA1(392214cc6ed4155bfe022d36f0f86c2594a5ab57) )
ROM_LOAD( "gorf-e.bin", 0x8000, 0x1000, CRC(2d456eb5) SHA1(720fb8b48e20c1fc281d8804259016c3c5364a07) )
ROM_LOAD( "gorf-f.bin", 0x9000, 0x1000, CRC(f7e4e155) SHA1(9c9d6d3bfee6556dc7a01de81d6148dd02f04fc9) )
ROM_LOAD( "gorf-g.bin", 0xa000, 0x1000, CRC(4e2bd9b9) SHA1(9edccceea5af015275582553ed238c40c73d8f4f) )
ROM_LOAD( "gorf-h.bin", 0xb000, 0x1000, CRC(fe7b863d) SHA1(5aa8d824814ee1c30eaf0044da78d3aa8220dcaa) )
ROM_END
Two ways to do this: Put it all one after the other in a 27256 EPROM or space it out across the 64K space of a 27512 according to the memory map from MAME.
After that, decode the address bus where it would activate the OE* line at the right time... keep the CS* line low... and it should work.
I'll have to sit down and see what makes sense for decoding the address lines. I've never programmed my own PAL or GAL chip but that would probably make it a much cleaner mod.
RJ