I personally would keep the 235. SBC engines are like belly buttons. Everyone has one!
X2
Find a 261 (lots of threads on this forum), paint it gray and very few will ever know. Think long & hard before swaping out the 6, the number of unmolested factory sixes vehicles is going down and even if you get a period correct 283 it still isn't a factory V8 if you go to sell the rig, IMHO ofcourse.