Help XS250 1977 vs 1980

Hi guys,
I recently got a XS250 from 1977. In an auction I got another one from 1980 for faily cheap (spare parts never hurt, right? ). I thought I would get the same bike, all I see online is the 1977-1980 1U5. I picked the 80 up yesterday and found some differences to my 77:
-Headlightbracket and aux light
-Handlebar is lower on the 80 (could be aftermarket)
-77 has the left fork with tabs for a brake caliper
-77 has disk in the rear, 80 has a drum

So my two questions are, is the fork the same except the brake caliper tabs and are there any other differences I havent seen yet?
Thx, Andy

 

Thanks, I've found this site, but either I'm using the site wrong or there is only one XS250 model. I only see this 3N6, where as mine is a 1U5. And they only have the model with the drum brake.. Is there an other parts catalog?

 

Thanks for the ebay link, aparently switzerland is not in the world of this guy, he shipps worldwide but not to switzerland

So I took the '80 apart and compared the parts with my '77. It looks like they share the engine with intake/exhaust and the fork with wheel and fender (except the '77 is ready for a second brake disc and caliper). So I think it is not realy suitable as a parts bike, I will build both and sell the one I like less.. Even fuel tank, seat and foot pegs (position) are different.
I did drain the oil on the '77 as well, it was mostly fuel