1989 MK IV Silverton Engines

After 2600+ hours, the engines finally quit. They were done, unable to exceed 3100 rpm, and finally overheating. I've bought two long blocks from ProMar, arriving next week. Also the entire cooling system was shot, the cast iron pieces no longer usable.
So, a total new cooling system, and rebuilt engines, assembled by ProMar with Comp Cam torquer cams. They were able to find a reverse engine cam, as well. It is a daunting thought to put all this together. I'm into this many $1000's, obviously, and running out of cash. How could I tell if the harmonic balancers have slipped? Promar used gasket kits to install the parts that they did install, and sending the unused ones along. Is there any reason to buy Crusader exhaust manifold gaskets? I would think standard would be adequate. I bought a Crusader 350 -454 manual and will have it worn out, I'm sure. Any tips from the experienced hands here would be appreciated.
Mike

How could I tell if the harmonic balancers have slipped?
Promar used gasket kits to install the parts that they did install, and sending the unused ones along. Is there any reason to buy Crusader exhaust manifold gaskets?

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Ayuh,.... Just compared the balancers,... If both are Exactly the same,.... Use 'em,....
No way, both slipped the exact same amount,....

Crusader don't make gaskets, they buy 'em from other manufacturers,.... Use what ya got,...
I prefer Fel-Pro gaskets myself,...

Ya say the motors wouldn't rev up, 'n overheated,..??.....
That Sounds like a lean condition for poor fuel flows,....
Go through the Entire fuel system, Before ya fire upp these brand new motors,....
Or,.... They could become new Junk motors in a very short time,...

Yeah, a lean condition was definitely one of the indicated causes. However the cooling system was shot, there were obvious leaks everywhere and the previous owners hadn't used antifreeze, due to always having to add water. As a result the "water" in the heat exchangers was black sludge. I replaced the fuel pumps just in case but no joy, the plugs looked ok, and compression was down under 100 in all cylinders, some as low as 85. I've replacing the worn out quadrajets with Edelbrock marine, as the carb guy said the shafts were worn and would not be cost effective to fix. Also one was not marine, probably off a truck or something. This has been quite a ride, and its not over yet.
Re the balancers: do they age/slip in one direction relative to rotation, and if so the reverse engine balancer would be going the other way?

Assuming the engines were assembled properly and the cams are matched, I'd say follow the builder's directions to ensure there are no warranty issues, especially with the cam break-in procedure....retorque the exhaust fasteners once things have run thru a full temp cycle. and 2X on bondo's recommendations...finally, use the manual - period....rarely is there a good recent to deviate from it....

Thanks, for the good advice. RTFM always a good thing, although all too often ignored!

I've replacing the worn out quadrajets with Edelbrock marine, as the carb guy said the shafts were worn and would not be cost effective to fix. Also one was not marine, probably off a truck or something.

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Ayuh,..... No mention of the hulls side of the fuel supply equation,..??.....

The Tank, Fittin's, 'n Lines are also, Suspect,.....
Especially the tank's diptube, 'n anti-siphon valve,....

Are the distributors original Prestolite with mechanical advance? If so they need to go as well. I used Davis Unified Ignition units with new wires and AC Delco Platinum plugs. Hate to spend all your boat bucks but the U coolers should be replaced along with hoses and transmission cooler hoses.

Is it using a thru hull raw water pickup? Adding a good sea chest with a strainer you can service topside now is the time while your engines are out.

You can pull water for a livewell from the sea chest also!