seem to have several choices that would fit in the GTV buckets, and run off about 12V (no amber lenses that I saw, however).
I think the stock fog-light fuse is 16A, at least for a '69 US GTV. This means that you definitely shouldn't go over 70 Watts for each bulb. I think if you use the stock wiring, you probably should not exceed 50 Watts per bulb. Even 50 Watts may be pushing it a bit.