What were your Blackstone results on the engine currently in your 93?
Since your 93 is still running, I would tear down the spare, clean up everything, and make sure it's good while it's out of the truck.
I would pull off the head, and have it sent off for pressure testing, cleaning, new seals, maybe lapping or regrinding the valves, and flatness, milling if necessary.
I would check out the condition of the cylinders and rings. Mic the bores to make sure they are still within tolerance and there is no rust pitting from sitting for a very long time.
I would flip it over, pull the pans, and plastigage the mains and the rod bearings, to make sure they are within spec and the journals all look good. This would be the time to replace all the seals, hoses, filters, gaskets, etc.
Then reassemble and lube everything so it is well lubed for long-term storage. Then, when the time comes, pull the old one, drop in the new one, and make fire!
We recently did this with a 70 GMC K2500 and pulled the engine to evaluate the internals. Turns out the mains are gone, the main journals have some grooves, and one cylinder has some scarring in it. By the time we would get done machining it, it was less expensive to purchase a NEW crate motor from GM than it was to machine and rebuild the old one, not to mention a LOT less time.
We should make fire in it in the next 60 days.
