What was the last year for the slant?
No the 3.8 is 70's era tech with pushrods. The northstar is a 32 valve overhead cam v8. The northstar is normally 4.6L, but in the oldsmobile intrigue and aurora they had a baby northstar. These engine were a 4.0L v8 and a 3.5L v6. The most important thing to know about the northstar is they are a pain to work on and you don't ever want to try to fix them when they leak oil.
The Northstar engine's claim to fame was that it was a DOHC design with 4 valves per cylinder, the first such V8 for Generic Motors.
The 3.8 (or, more recently, "3800") V6 motor dates back to its origins as an all-aluminum 2-valve-per-cylinder V8 that was 215 cubic inches and went into the Olds F-85, the Buick Special and the Pontiac Tempest, compacts for G.M. in 1960 or '61 (can't remember which; I've slept since then.)
As with the slant 6, the aluminum construction didn't prove to be somethg they wanted to deal with, long-term, so the engine construction material was changed to cast iron after while,
Aftwer that, a V6 version was created by hacking off two cylinders, yielding a vibration monster.
The V6's that are in good balance, inherently, employ a 60-degree V angle. This engine was a 90-degree V8, and there was no reasonably economical way to change that design parameter, so they lived with the vibration... for a while.
They designed a crank with rod journals that were built so that connecting rods on a common crankpin, had different orientations (locations) that took away some of the geometrical imbalance, and made for an engine that had a more "even-firing" reciprocating assembly. They designed and built special motor mounts with excessive complicty, giving the engine a soft cushion to sit on for its still, not smooth, gyrations.
Finally, a big redesign resulted in the addition of balance shafts to further quell the engine's tendency to want to jump out of the engine compartment....
Eventually, and after many years, this "once a V8, now a V6" motor was smooth enough to power most anything G.M. had to offer, so it lived a productive life in a variety of vehicles, but not without having hosting a boatload of technical advancements, over its long life.
It has no ties (engineering-wise) that I know of, to the Northstar.