will trx250r shocks fit my 99 blaster?

For the rear shock, go to kenoconnorracing.com and buy his bushings for the year shock, because the shock will be to thin without them. Comes with the extended bolt. And both those are very good deals, pick them up.
 
front shocks ...no
rear shock....maybe, most likely doubtful, depends on length and if you like the trailer park, jacked up Camaro look ?

stock 34mil carb ?
stock to what ?
all, larger carbs are jetted too rich for a blaster, will/may require different pilot, needle and main jets, possibly the slide too.
if you don't have serious engine work done and matching mods ?........ stick with the stock mikuni 26mm carb