kaw rider, the new rad is w=4 1/4", h=8 5/8", d=1 5/8" . the stock 250 rad is w=4 1/4" h=8 5/8" w=1 1/4".
i have some stock 500 rads i can measure but im sure you have some too
i think the new ones are more than upto the job, do you think the will make the motor run too cool?, also the rad system on the new bike will be in parallel compared to series on the the stock 500, how do you think that will effect it.