The original 216 in my '51, 3600 truck is in pretty good shape. The side cover leaks a bit but I've replaced the front and rear main seals and I don't mind adding a bit of makeup oil occasionally. It doesn't smoke or make any odd noises and it starts and runs just fine. It's a add gas, check the oil and go sorta rig.
Well, I've been considering a 261 upgrade even-though I'm pretty happy with the lit'l 216. A bit more ump would be nice when running in the hills or against a headwind. All that said I just stumbled across a '59 261 in a shop that was pulled from a old wrecker 10 years ago when the owner wanted a V8. Engine has been in a corner of the shop since then. Represented as ran fine when pulled. Price is $200.
I'm thinking pull plugs, squirt in a little oil, if it turns over pay the man and set it in my shops corner while I assemble the odds and ends for the swap. From following other threads I know the water pump will be an issue, I may need to swap the crank pulley for belt compatibility but can anyone speak to motor mounts, exhaust, anyway I can (without breaking the bank) keep my foot starter?
It does seem a bit foolish to pull a perfectly good original 216 but nobody ever said I wasn't foolish

Picture of the engine, looks to still have a carb.
More info, I haven't seen the engine yet, just the one photo. I'll look at it early next week. Other than will it turn over, one of the first items is determining if it's actually a 261 or a 235. Guess I'll need to be armed with engine numbers and a few details for proper id'n in my head. Good thing is I should have good cell signal at the shop so it may be as easy as Googling the engine number.
RonR