if you modify a GS it would become less reliable same goes for the Road Master.
If you really want to increase the over all OOMPH of the bike engine swap for Road Master with CB250 can be safe play option and for GS you can go with a GN250 engine..
If you have spent a lot of time with people who are into this kind of stuff the any modification you will do will make no harm .. but if you are not very much into technical details of bike it will be a very bad idea... money, time you fantasy every thing will end up for nothing.
Just remember the Stock vehicle is the best in the given design possible designed by Pro Engineers out there, any changes we do will only degrade it unless any well experienced do it will well depth knowledge.
I altered a Road master back in 2008/09 I invested 200k roughly and 3 years of time over all including every thing but now I know it could have been done under 50k only ....
So stick to some good mechanic for fair advices, and keep Pakwheelers in loop to so may be we can come useful to you too as many modification magician master I have seen here...
hope it helps.