The 230 should be fine. With the 250 you would only be gaining 20 cubic inches so not much there. At some later date if you really can't live with a stock truck and want more power than you can go the 350 route and p.s. is easy to find for those. You can then sell your stuff at a good price.
fyi: I got mine from an El Camino about 15 yrs ago. I believe it was a 69 or 70. Problem is I didn't get everything so I had to scrounge for another 6 months. I finally went to the dealer and he happened to be able to order a bracket that I needed.