I'm not sure if anyone had HIDs in the 1980s, and if they were around I'd bet the crufty old US DOT had not yet authorized them for street use in the US.
I'm out of touch with what's available now, but in the '80s you could get aftermarket 7" units that used halogen H4 elements, but they were only approved for offroad use by DOT. They would fit most any American car with 7" headlight buckets easily. Hella, Cibie, Carello, and other companies made them (and they were legal in Europe). You could also get them in motorcycle shops; back then many bikes used standard auto-sized headlamps.
My Dad had 7" Hellas in his GMC pickup and they worked well. After one was broken by local street trash on a fun run we replaced them with Cibie 'sealed' units; those still used and H4 element but had an inner glass globe around it so the reflector unit was truly sealed. They didn't provide as nice a pattern as the Hellas, and the bulbs burned out faster, we think because they ran hotter.
I never had 7" Carellos but I ran the 5-3/4" units in my Challenger for years, and the light output was excellent, but they absolutely required a relay to power them, especially with the high beams on.
Heh, just looked up a Hella catalog. They've got two 7" round conversion headlamps now; the old H4 based unit which is still offroad only in the US (DOT still hasn't got past the acetylene lamp stage in some ways) but they also list some that use the newer style 9003 bulbs and those don't say anything about offroad only. I'd bet the light pattern isn't as nice as the H4 units but it'll still be better than your average sealed beam, even a halogen one.
http://www.hella.com/produktion/HellaPortal/WebSite/Internet_usa/ProductsServices/PDF/Headlamps.pdf
