Originally Posted by rbm
As promised, I'm updating this thread with my experience so far.
Based on the great information I received, I contacted my local Part Source store (this is a Canadian aftermarket automotive supplier chain, part of the Canadian Tire brand) and asked about 7" round headlights for a 1972 Datsun 1200. They came up with a Hella Vision Plus 176mm HB2 Conversion Headlamp (part number 1A6 002 395 301 ). I ordered this light and received it yesterday. It fits the headlight bucket perfectly for diameter, however there is a 5mm gap between the back of the reflector and the shell. I will have to find a gasket material to fill that gap to provide pressure to stop the lamp from flopping about. The unit has a flat solid glass lens with very clear beam focus. It appears to take a standard H4 halogen bulb however it is supplied with a HB2 bulb for D.O.T. purposes. It is a very good replacement for the Slash 5 lens/reflector assembly. The only drawback to using this part is that it does not have a small bulb that can be used for a parking light. I will have to think about how I will solve that problem. I can post some pictures later when I have figured out the means I will use to secure the headlight assembly in the bucket.
Thanks very much to everyone who helped me.
hmm, so headlight spring clips won't work?? that is how the lens is secured on many bikes. Have heard that there are 7" H4 reflectors that do have parking bulbs, many use them on British bikes, the original Lucas items had parking bulbs too...