Just to echo the comments about the block casting numbers -- NEWS FLASH --
***** Not all 261's have Captain bars *****
The other thing is .... DON'T ORDER ANY PARTS UNTIL YOU KNOW BOTH THE CASTING CODE ***and**** the DATE of CASTING. It matters!
At any rate, if you find a 261 without captain bars, the casting code will tell you what it is -- either a block cast in 1954 or 1955, or a later block cast in the '54 mold. In the OP's case, if he's found a later 261 out of the '54 mold, then he's found a crate motor that was built as a replacement engine for the '54 and '55 first series trucks. What that further means is that it is a perfect upgrade engine for the AD trucks as it has the higher water pump position and fits in exactly without modification. So actually, for a pre '54 AD truck, the non-captain bar 261 is the one to have as it will require zero modifications to fit and work perfectly in your truck.
I pulled a perfectly fine 216 out of my 3804 and replaced it with a 261 -- it was a group effort and we made a pretty good tech tip out of it (
read it). The other thing we learned was even though it seemed to run fine, you need to treat every unknown engine as a rebuildable core. It was making a particular noise at road speed that only Hotrod Lincoln could hear, and based on his recommendation, we pulled it back out and tore it down -- sure enough, the crankshaft and cam journals were heavily scored and number six piston had a few chunks missing out of it. Had I continued to run it, it probably would have catastrophically failed. Thanks Jerry!! Ended up having the crank ground and getting a new cam.
On mine, I used all the peripherals from my 216 (except the carburetor) to make it look like a 216, including the bell housing, flywheel, starter, generator, fuel pump, valve cover and distributor.
Sure, with care, the 216 can continue to run in your truck, especially the little trucks. But for the 3600 and 3800 trucks, at least with mine, driving in traffic or hilly conditions was problematic with the ole 216. Great engine, but not for a heavier truck in modern traffic -- especially with the HO52/72's original gearing. Oh yeah, so while I still hadthe 216 in my truck, I switched out the third member for the 4.11 gearing. Great, the 216 could now get me to 65 mph ... but the slightest hill or headwind, and we were back to 50. She huffed and puffed but holding speeds higher than 60 were pretty hard. Plus, accelerating from stop lights, or trying to pass anyone were exercises in futility. The 261 has reinvigorated my truck and has made it a lot more able to share the road with modern iron, if not also safer (people aren't doing stupid things to get around me). We will all support you if ou want to stay "original" but I wager you've already crossed that line somewhere else
Why not at least make the truck driveable on modern roads?
If you do get the 261, do yourself a favor and tear it down before you install it. Chances are, if you don't, you may end up having to pull it back out to do it anyway. Worst case? You find nothing wrong and you slap it back together with new seals, bearings (why not, you have it apart anyway??) and gaskets and a whole lot of peace of mind.
One other lesson learned .... don't order new main bearings until you pull the old ones to see which style they are ... We talk about this one in the Tech Tip ...
IF it is a later block cast in the '54 mold, it will probably be set up for the later bearings (dimples) rather than the early bearings (dowels). Not wanting to wait for a new bearing set to come in (and having everyone standing around my shop for a week ...), Jerry whipped out the drill and modified my block so now it will accept either style main bearings
(which was nervewracking to say the least -- watching someone take a regular power drill to the crankshaft journals ... freehand ... but it worked!)
Just my opinion from having been there and done that.
Oh, and did I mention that not all 261's have captain bars??
