Have you run a compression test, to verify the engine is up to par? I ran a 55 1st with a 235 for several years, and it got weaker and weaker. Finally ran a compression test which told me it was time for some attention. When I got the head off, I found 3 burnt ex valves, which meant that I was basically runnig on 3 cylinders. I ws still able do run at a decent speed on the freeway. After the rebuild, I put a 3:38 to one ring and pinion in it, and now I will be cruising down the freeway with the wife following me, and she will call me on the cel and tell me " Hey your doing 85 or 90. You better slow down or you're going to get a ticket." The 235 has plenty of power as long as it is in good shape, but as it wears and loses compression, it also loses power. A compression test is easy and will tell you alot.
