I have used a SMT 603 LED and mounted it into the castings and then filled with clear epoxy. Might take a few trys but you can get a dome shaped lens.
one more thing, make sure that the LED wires are insulated so you don't have a short befor you fill .
I'm working on this loco and obtained a Cal Scale Pyle headlight (see link) and bracket to mount at the top of the smokebox door.
a) I think a SMD (0603 or 0402) could be added inside, with wires coming out the back if I drill a hole. I'm assuming that is the best LED option?
b) The opening for a headlight lens measures about 4.25mm, 0.0167". That would be 14.5" if multiplied by 87. Can you recommend what to buy, type & size? I see several brands on EBay, and wonder if I should use a curved front type or a simple flat piece like a glass. Or find a light pipe piece of the right diamater?
http://www.bowserorders.com/.sc/ms/sch/ee?search=190-331&go.x=14&go.y=14&go=go
Any suggestions are most welcome, as I may be stretching well past my expertise here.
Paul
Modeling HO with a transition era UP bent