I'm a complete zero when it comes to 1st-gen LUVs, but I have a P'up (= to a 2nd-gen LUV).  I put a GEO/Suzuki dome light in mine and it's great.  It mounts flat, so you don't have to cut out a recess to accommodate the socket.  I used one existing mounting screw-hole, and drilled the other.  The light came from a Metro, I think, but it was the same as the one in the Samurai and probably the early Tracker.  It's brighter than my factory light was, too.
Jack
					
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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.comIsuzuPup.com