no, that wouldnt be good for a ported engine with more power let alone a big bore. Thats for a stock 98-99 srx700.
what year srx are we even talking about?
who is doing the work on the engine? amount of work done/power output will determine where your engine rpm will be, ask your builder......
why would you use stock srx weights in a modded engine??, kinda defeating the purpose.... you should use something to clamp the belt to take advantage of the new power.