What small cam do I have???

If it runs good like it is. Use the same parts. The biggest problem with cpls is the biggest majority of old good running engines were done by mix matching parts. In these parts old timers used to what we and ZZTop call “Coon Tune”. In other words. Top secret sects of the trade. My uncle tuned the pump and timed the 350 in my Pete. I have no clue what it is set at. It runs good, does not smoke, starts easy, pulls good and gets 6’s for mileage. I had the pump rebuilt 10 years ago.due to epa the Pump shop had to put it back as a cpl160. It ran down on power and got 5’s. They gave me back all the modified parts they removed from the pump. I put them back in after their year warranty. Other then the #7 button i have no idea what the spring color codes were, but It is nowhere near the cpl 160 it was born as.
Cummims NH’s are like smsll block chevys. Easy to work on, modify, snd ain’t none of them “stock”.

 

Front of the motor, should be a lever, usually removed the cable to avoid any…. Issues, with drivers, but leave the lever so someone can still get it started with a second person

 

Yes, piston coolers.

 

I wouldn't worry about the plug. Original one most likely corroded and went to leaking. I have a few heads that have had threads cut into a hole or two and been pipe plugged.
You have original Model 25A Jakes. Those have become very rare over the years because a very small percent of engines had them back then. Newer Model 425 kits will work on them in most cases.