What a relief!! I am glad it was the "lawn mower" syndrome, oil pressure not high enough to lift the hydraulic valves and you have valves in the half open/closed state -- zero compression. The only way to fix it is to crank the starter, with the pedal to the metal, until it starts.
Yes, the manual tensioner needs to be adjusted correctly, otherwise the belt will cause undue stress from being too tight.

The cam locking tool from IPD only works for 93-98 engines.

And I agree with your mechanic, there is a difference in parts. That's why they can charge less. And why don't you have a good thermostat, where is that wet noodle :)

I am sooo happy for you,

Klaus

PS. I think we deserve a beer!
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1975 164 w/174,800mi (Sold) 1995 850T w/91,000mi, 1998 V70R w/129,000mi