My vote is the belt. Cheap fix vs tearing everything apart.

What were the compression numbers?

While you're at it, Bring it to TDC and check if the timing pointer still aligns. It's not likely but I have seen broken or missing crank keys, just something extra to check.

Just an idea... maybe internal blower failure??

I’d think smell a slipping belt after running for any length of time but sure would be nice if that be the culprit. Leak down!!!!

We just dynoed my LS setup. and lost 1.8psi from first pull to second pull then held consistent. Had rubber dust behind pulley. Check your belt. Definite pissibility

The compressions numbers varied from 85 to 90 PSI per cylinder @ 6500' elevation. Before the blower installation I believe the compression numbers were closer to 110 per cylinder. The blower belt only has about 20hrs on it & no signs of belt dust anywhere. I did get a leak down tester but haven't had time to test yet.

when U say no boost is it 0 PSI? I know very little about blowers other than it's an air pump. Is there anything inside that can cause no boost such as seals or the drive to turn the rotors?

110 psi at 6500-7000' elev is around 135psi sea level. That's ballpark for a blower motor that's intentionally built with lowish compression.
90 psi is 110psi sea level which indicates a sick motor. You'll be lucky if it's just head gaskets.

Belt slippage can happen with no obvious signs, but you need to resolve any longblock issues before you go any farther.

I assume both compression readings were done with slightly warm motor and throttle wide open? If not, you could have test variations affecting the readings.
Leakdown. Do a good leakdown. Either have it done by somebody trustworthy or have them there to assist you.

M

I did the leak down after watching a utube university video. I pulled the plugs, inserted the hose into the cylinder & bumped the starter till I felt the compression build. Then I hooked up the the leak down tester & read the gauge. All the the cylinders were in the high 40's to mid 50% range. You could feel & hear the air coming from the valve cover port. Is this beyond just replacing the head gaskets?

Never a fan of the leak-down test. Either it holds or it doesn’t. I do a compression test to look for low cylinders. From there I pressurize that bad ones to hear where leaks are coming from... intake or exhaust... head/valves. Coming from the crankcase (valve covers) rings or a hole in a piston.

In your case ... sounds like the lower-end is tired sir. Rings or holed piston(s).

Wish it was better news.