I think yours is one of the most creative engine upgrades I've read on the forum, Boxcar. It is out of the box and I really like the simplicity and durability of the engine you used as well as the cost of repair parts for it.
My only Datsun experience was with a friend of mine in high school who drove a little '70 or '71 Datsun pick-up truck that his father had bought. We cruised everywhere in that little pick-up for a couple years and my friend was absolutely murder on it. He drove the piss out of that little truck. Burning off the tires, high speed down shifting, just basically abused it all the time. He was one of those kids who never really appreciated the cost of things. If I had been his dad I would have taken it away from him... but that little truck (and engine) took all that abuse and just kept going. I still think about Gary and that little truck ever once in awhile and I am still amazed at how well and long it ran.