I added one of the underhood lights you mentioned to my '82 GMC (full size) Jimmy just after I noticed one on a new '88 GMC truck. I ordered it directly from GMC parts. In addition to the on/off switch, the remote light had a magnetic base that could be placed anywhere on the vehicle. What a trick little piece. I could even place the light on the tailgate of my Jimmy!
Thanks for reminding me, I was discussing this not too long ago with Rob Hanson, telling him I intended to order another one for my Dodge Ram.
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'98. 5 2500 QC 4x4, (BLACK) SLT Sport, ISB, LWB, 3. 54 LSD, A/T, Glasstite Vision II canopy, Line-X spray in liner, 285/75R16 BFG A/Ts on 16x8 M/T Challengers, Warn 4X Boards, Mopar fender flares, front and rear NW Custom stainless steel/rubber mud flaps, Mag-Hytec diff. cover and trans. pan, Edelbrock IAS shocks, Mopar tow hooks, Reese Titan V hitch, Jordan Research Ultima 2020 trailer brake controller, VDO Vision gauges, '00 Sport grille, '00 Sport headlights with PIAA Super White 9007/9004 bulbs, 4-2-7+4 Brite-Box, PIAA Dual Sport 900 auxiliary lights, BD exhaust brake and TorqLoc, Prime-Loc fuel filter relocation kit, Bosch 275 hp. injectors, VA CPC, DD Boost Module, Banks Stinger wastegate actuator, BLACK '00 valve cover, Banks Stinger 4" dia. stainless steel exhaust system, BD LV V10/Cummins hybrid TC and valve body, BD modified transmission front pump and PressureLoc, plus many other trick modifications