In the 13T right now is a 11,000,000ish serial number block which puts it in the January '25 production range. The block that belongs with the T, 251,xxx, was removed as one of grandpa's projects to be rebuilt/worked on. The block project (whatever it was) was never completed before it made its way back into the T.

A couple of questions.. is there a difference between the '25 and '13 T blocks I should be aware of? Different parts, head, or some setup that would require finding those specific parts if I was going to put the '13 block back in? (FYI, I didn't see anything obvious, like a starter, under the hood)

With the 13 block already out... is there some things I must or should do to it while its out? I've never restored a car before but have worked on cars. So I don't know things like how to ensure the block is good in the first place... but I do have the ability to put the block in and get the engine assembled.. etc.

My first priority is to get the T back to driver status, which I don't think should be that hard. Grandpa had it driving until he was unable to work on it anymore. But I'm unsure of any work he was doing on it between the last time I saw it running and now... so I don't know if he was in the middle of something.

Just curious with all the T blocks laying around a while back (e.g. there was a '14 block in the same garage the T had been stored in).. wondering if there was a difference between T blocks that might make one year preferable over another.

Darin

Many, many differences. Some are major, some minor. One of the big things, is simply horseless carriage status for the HCCA, if that matters to you. The biggest change in the casting, is the provision for a generator in 1918/'19. Another, soon after, but with a lot of crossover, is changing from two small valve covers to one large one.
A smaller change between 1913 and 1914, is the (commonly, and incorrectly, called) freeze plugs under the exhaust manifold. In 1913, they are threaded and screw in. In 1914, they became the simple "press-in-and-dimple" plugs used till the end of T production. (I am ashamed to admit, that with all the minutia rattling around up there, I don't know the correct term.)
There are several other minor changes including whether or not there is a Ford script on the side of the block. Location and method of dating the casting. Size of the serial number embossment. Minor variations in mold markings, separations and water jacket radius.
That is all the block. The other important things for a proper '13 engine also include an aluminum hogshead with lettered pedals, a "low" head, and "narrow-nose" pan.
It is sometimes advisable to use a starter type flywheel as it fits in okay, and if for any reason you or a subsequent owner need to add a starter, it is an easy change. There is no need to change the block to a generator type as there are simple ways around that.
Just off the top of my head.
Drive carefully, and enjoy Thanksgiving! W2

Darin,
One addition to Wayne's list of differences,at the back of the block there is a lip at the water jacket which matches the lip on the cylinder head. Later blocks taper from the bottom of the water jacket to the block surface without the lip.

Allan from down under.