I do make some custom parts for the SR. I know the parts for use for making rearsets. I may make a few rearsets for Them in the future. The forks need to get dropped internally and uprated fluid viscosity for serious road use.
The RFY 130mmm rear shocks work great with these bikes. Tank swapping is a little limited only due to the back bone arch of the top tube. Wheels from many yamahas fit.
There are plenty of cheap ebay parts for them, 31mm clip ons ($30), headlight/fork ears ($10), bar ends etc. etc.
My favourite mod is the brass fork caps mated with 12 gauge shotgun shells where the bars were (you use clip ons)
I'd like to lose the stock yamaha controls one day and have a horn, starter, high beam and kill.
And the kick start. XT250 is you best hope for a donor. It's a quick install but don't forget t buy a dowel pin for the kick spring. The SR doesn't have one. I made one on my lathe in the time it took to walk back in the house and order one.
You can really dress this bike up due to it not having too crazy of a parts range. Lots of cross yamaha availability and 31mm forks are not out of the norm.
But my best advice is ditch the tank if you want cafe. MY tank is a seriously modded Suzuki gt380 tank.