i think you are talking about RXZ135 engine swap,
you know nothing would be better then stock, if you have good engine of 115 then go for it,
coz in future you will have to need engine and electric parts and in the market 115,s part would be easy to find,
one thing more if you are going to restore your bike (body wise) as stock bike then rxz engine will not suite it, but if you wanna speed n thrill on rugged looking body like cafe,s then go for rxz engine, but i tell you the real taste of rxz engine will have if you would have its other related parts like carb of rxz(55k or 5pv) cdi of (55k) ignition coil(3v6) and the most important thing its expansion chamber exhaust,
but if you would install only rxz engine with collaboration of rx115,s electric parts like cdi,ignition coil and also the 115, carb and exhaust then there would be lot of head ache
falt response will have in the end
so decision is your,s
i think there is another rx with rxz engine in Bahawalpur , its colour is red and one of my friend Sannan showed me
