Loved my first Bonnie.....'90 with 358,000 miles.
this one is killing me. UIM problem both times. I found a motor at a salvage yard from another '95 (so I was told). I sent my son to pick it up. He took it to a buddies garage where it'* been under a tarp since March. We uncovered it last night and realized that it'* not a Series II. Will this be compatible with the '95 electronics or do I need to go find another engine?

To be totally problem free you do want to stick with the same year.

You probably have an L27. Not compatible with your L36.

Any L36 from 95-current should work fine for you.

In case you didn't pick up on Bill'* acronym affinity,

L36 is Series 2 naturally aspirated
L27 is Series 1 naturally aspirated

he might also have a Series I SC, since its out of a 95

While the donor motor is still out of the car is a great time to replace the crankshaft seals, water pump, and the manifold gaskets lower and upper like jr's3800 suggests. You should also replace the plastic bypass elbow on the lower intake manifold with a metal one with new o-rings. If the new engine is from 95-98, I would also suggest when you do the upper intake that you sleeve the upper, install a reduced diameter stovepipe, and a 180 degree thermostat.

Lots of information you can search on this site on how and why to do this stuff.

The extra time and money invested are insurance against the most common failures with this engine.

I talked to the salvage yard owner about swapping the Series I for a motor from a '95 or newer. He said it'* the same motor and all I really need to do is switch the intake. I'll admit that I'm certainly not well armed enough with knowledge to present a strong enough argument to make him understand my side. That being said, what kind of issues and costs am I looking at if I had to make this motor work in my '95. Would it run right with the '95 electronics and tranny....ever?

I think the peeps you're talking too aren't checking their books very well. The S1 (L27) was put into the other h bodies (olds 88, lesabre) in 95, but the bonneville got the S2...

So to do a swap, you'd be looking at the full wiring harness and PCM from an 88 or lesabre, versus getting the right motor and dropping it in. And I think you'd be a little dissapointed with a S1 after having had the S2 (personal opinion).

Otherwise, how bad is the engine that is dead? Did it sit with coolant in it for long? GM has come a long way on upgrading gaskets and whatnot to make the S2 a LOT more durable, starting with LIM gaskets that are now sleeved to prevent the damage that they so commonly have. And they've made changes to the UIM gaskets, as well as the EGR stovepipe, that all extend the life of the S2. It'* not perfect (yet), but a properly done job should last you a very long time...

The not quite dead motor has a lower engine knock (crank) along with metal shavings in the oil.