1940 B Question(s)

[Texas Tony]

First, let me thank everyone in advance because I would have never decided to tackle this project without previous help in this forum on another tractor.  That being said, let me pose my questions with some background.

I have a 1940 B, serial # F.A.B. 40150 that arrived on our farm close to 20 years ago after a neighbor traded it to my dad for some work.  Long story short, it's been sitting for nearly 18 years and is now in my barn in pieces.  I have the engine apart and crank and block both sitting in electrolysis tubs, and will hot tank them probably in the next week or so, including the governor, carburetor, and everything else engine-related that I can get into the tank to clean up.  Suffice to say that this will be a pretty thorough refurbishment since I plan to put this tractor back into light duty cultivating our garden and small jobs around the place.  So, here's the fun part:

1)  I don't see a problem with buying a complete overhaul kit that includes valves, gaskets, etc.  Or should I not?  I've never done this before so I'm asking the experts, here;  this will be my first engine overhaul, but I've grown up working on equipment, have toolboxes for of tools, and a nice barn/shop to do this in, so why not.  If you had to buy a rebuild kit, whose would you buy and your thoughts on the product(s).

2)  I've also read that step-head pistons are better if a tractor is going to be working.  It may wind up in our local parade, but that's once a year- the rest of the time it'll be wearing double-row cultivators or pulling a planter.  What are the pros and cons of step-head pistons? 

3)  The radiator:  while taking it off, one bolt on the left side (while sitting on the tractor) was rusted smooth off and pretty much disintigrated when I took the radiator off.  The other broke the whole piece of cast-iron off from the block that it was bolted to when it came off.  I'm thinking it had already stress-fractured at some point, but nevertheless, it's off.  Can a good radiator shop replace those bolts in the bottom, or am I looking at a new radiator because of that issue?  When I drained the radiator, it was still green and was not leaking anywhere, so at least I know the core is still in good shape. 

I'd like to get some answers before I start buying parts this week, and I wanted to bring my concerns here because I trust the folks in this forum and value your opinions.