I agree with OnAnySunday about this bike, except of course that the RT would be a descendant of the old DT, not an ancestor. I and many of my friends had bikes like this when we were youngsters, we had a blast on them. If you really want to make some modifications to this bike, you will have to be a little creative and do more work than on other bikes.
If you really want to dual-sport the bike, you can probably do it with junk yard parts. DT175s or IT175 or 200s had ignition systems with lighting coils that will PROBABLY bolt into your RT. (Check before you buy!) The lights can also come from the junkyard, or you could use universal parts from the aftermarket.
Hi-performance reeds for a DT or IT will probably fit it, too, if you can't find a listing for the RT. Again , you will have to measure to be sure they will work.
Check out the Boyesen site for the reeds if you are interested.
I know the IT200 top-end parts will bolt up to the IT175 engine; they may fit your RT as well. They would give a good boost in low-end and mid-range if they do.
You would have to be a fairly decent mechanic to make stuff like this work, or have somebody who is to help you. The worst thing you could do is to start tearing the bike apart, find out you're in over your head, and have to pay somebody big bucks to put it right again, so be careful!
When it comes right down to it, you will get the most fun per dollar out of this bike by riding it just the way it is. I hope you have as much fun with it as I did on my first trail bikes!