Panic -- Actually, if you find a 261 block from the 1954 mold, it *is* a direct bolt in as 1954 mold engines were designed for the '54 and 55 1st series trucks so the water pump is in the correct position for Advance Design trucks.
For the OP, I went from a 216 to a 261 and I couldn't be happier with it.
Here's the Tech Tip we all worked on about this engine upgrade and rebuildThe 235 is a good upgrade, but a 261 is even better. And if you can find the earlier 261, it's a very easy install. As I did, you can even dress it up with the valve cover and distributor (if you're staying 6 volts, anyway) from your 216 and not very many people will even notice that it isn't actually the original engine (unless they know to look at the carb or the pushrod cover
). And you will find that some self-professed truck experts are fun to mess with at shows and cruise-ins. I even used my 216's bell housing and flywheel so I could keep it 6 volts.
And BTW, numbers matching is nice and all that, but it doesn't mean quite as much to the old truck community as it does to the muscle car crazies
so feel free to turn your 216 into a boat anchor
Oh, but send your connecting rods to Jerry first
