Do the dye pen test after it has been tanked. Parts need to be very clean. If it passes, it’s already clean and you know the crack wasn’t obscured. If it fails, you know the cleaning made sure you found it.
It sounds like the only failure mode you are really worried about is the leak, which pretty much limits it to:
- Cracked Head
- Cracked Block
- Warped Block or Head, which if no cracks in the above, you would have surfaced as part of the rebuild and taken care of.
- Blown Head Gasket, which could be due to unequal tightening over time or warped Head/Block which above would take care of or when put back together.
If you weren’t having any other problems that would cause you to suspect a problem with crank or cam is damaged - then probably wouldn’t spend money to have them checked. Just me, but unless the journals are in really good shape, I’d have it reground to first oversize bearings.
The cylinder bore, if not scored, and within Original spec’s and pistons in good shape, I’d ridge ream off any step (makes sure new rings can’t hit something), rehone, and rering. If out of spec on bore, go to first oversize with new pistons (I’ve never had a resleevable engine I’ve rebuilt)). If there was some warpage on block requiring resurfacing, personally, I’d go to first oversize on bore to ensure they are straight and true.
Not sure what parts would cost, but Tom knows a great place to get those. You’d be way under the $3,500 and know the engine was put back together correctly. If the cam needs a regrind, this gives you an opportunity to “Tweak” the cam with a different profile for more high end, low end, economy mode, etc. I went crazy on one engine - added almost 3,000 rpm to top end, but wouldn’t idle below about 1,800 rpm (having the flywheel weight almost cut in half contributed to that - but rev’d fast)
The savings come from all the labor you are doing. I’ve replaced oil pumps at rebuild just becuase it’s out in the open and visible. But you can inspect them for wear also, if within spec (but not close to the limit) then you can reuse it).
If you can: GET A FACTORY MANUAL. Will set you back around $100 but is worth every penny and will save you money. I’ve enjoyed doing rebuilds, there’s great satisfaction, when you turn the key, it rotates a few times and kicks over. Plus you save some serious dollars and get a real education on the engine.
I’ll set a reminder. Beyond separating those bits though, I plan to slowly document, label, and sort everything as I strip everything at home. I can’t transport an entire engine home in my car, but I can if it’s in smaller pieces 
