I have recently got into body casting and am enjoying the handcraft that it involves.
Creating windscreens is usually done by vac forming although I have seen parts cast in a clear resin...windscreens etc.
The search continues for the rght materials. They are out there.
I have cast some clear parts using clear resin. To ensure that all air is out of the resin it needs to pressure cast, also the cure time is much longer. The process is the same as casting bodies. BUT be carefull when removing the parts from the mould many clear resins take a long time for the final cure on the surface,so finger marks can show easily. I usually allow for some spruce from the vent holes so the part are easy to handle.
I have cast resin headlights of different models but for a clear headlight look I use a disc of aluminium, punched out of a thin sheet, then a small blob of "five minute" epoxy/araldite put on the surface. Just enough to fill the circle gives a raised curved look.
I think I need to clarify, I'm not necessarily talking about just headlight lenses, per se, but the overall head light assembly front. I.E. a Lola T70 MKIIIB lens, with it's fancy molded cover that is integrated into the body, or an LMP headlight lens...
I think I "may" have found a resin suitable, but it would seem like you'd have to have a LOT of headlight lenses to have lined up, in order to use even a small amount of the resin...
I use a resin from a local supplier here in Australia. But search for clear or embedding resin should produce results for smaller Quantities, also check YouTube for tutorials.
I usually cast between 15 to 30 PSI in my pressure pot.
I also vac form a lot of clear headlight covers for my resins. I simply add the moulds to the glass mould and form it all in one.
As for your example of buckets and lights, I have done this type of assembly.
Headlight buckets are vac formed with the interior platform using styrene, head light covers vac formed in clear along with the glass and the head light themselves are resin cast in clear and chrome tape used to add a backing to the lens.