Carmen;
I have to pile on with Alvin and the others. I had the same thoughts as you when I bought my 58 Suburban. It does not have the original motor, but it does still have a straight 6 250. It ran pretty rough when I got it so I was convinced I would need a newer/bigger/better engine. I had visions of a hopped up 292 dancing in my head.
Well, a real good carb cleaning, setting the timing and addressing a vacum issue was all it took to get it singing. I have plenty of power to pull the big old beast around.
Get the 235 running and you will be satisfied. As was said above, gearing is the key to highway speed. You can either change the rearend or change the transmission to an overdrive unit. You can get some return on going to taller tires, but not a whole lot.
Bottom line: for a relatively minor investment I think you could get the 235 running and be very happy with the results. It's a lot easier to have philosophical debates about the future plans for your truck when you have it running and can use it. Gives you more time to think. Now if it turns out that your son toasted your motor, that is a horse of a different color. Oh the joys of parenthood. :-)
