The oil pump in both normal rotation and reverse rotation engines turns counter clockwise because of the cut of the cam gear and distributor gear.

A Melling M83 or something that cross references to it, is a good stock replacement pump for your engine.

A Melling HV83 is a bad replacement for your engine because it's a taller pump that hits the oil pan and keeps the pan from seating on the block which makes for an oily mess 

You're just fine with a stock volume pump

The first thing you should do is look at the rebuilt 78 engine which if it's the original block will have a 2 piece rear main seal and then look at the 91 which would have a 1 piece rear main seal.

If you reverse the rotation of the 78 to make it a normal rotation engine, you're gonna have a rear main seal leak.

The 78 uses a crankshaft that has oil control wick lines (AKA helix lines) on the crankshaft in the area of the rear main seal and the lines are backwards on a reverse rotation engine.

Here's a picture of the lines. This one is Reverse Rotation

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This means that instead of helping to keep oil in the engine, the backwards wick lines will help oil leak past the seal if you turn the engine the opposite of what it was meant to turn.

It's not just a minor leak either.

You'd have to put in a normal rotation crankshaft built for the 2 piece seal or get the lines removed by your machine shop.

The crankshafts won't interchange between the earlier 2 piece rear main seal engines and a later 1 piece rear main seal engine without some serious machine work either.

The front seal isn't as critical, and it can still be bought for either rotation direction. It has the oil control lines in the seal running on a smooth sealing surface on the harmonic balancer.

You might say that nothing is as easy as you'd like it to be. Numerous people here on CCF have run into this rear main seal issue on a rebuild or engine replacement when changing engine rotation..

You mention that you have a new heavy duty 1.23 to 1 transmission for the sport. Is it the later, new and improved PCM 80A or the original style PCM40A?  

You'll need some new unused lifters to go with the new cam. Maybe the 78 has never been run and it has new lifters, otherwise if it has been run, then the used lifters and the new cam aren't a good combination

The normal rotation starter from the 90 and the normal rotation rotation distributor from the 90 would swap over to go with the cam swap

The PCM 80A only works with a Normal Rotation engine, so you're good there. You can't use it behind a Reverse Rotation engine and do a prop swap unfortunately, otherwise things would be a lot easier.

So, you need to figure out the seal configuration situation and get that right in order to prevent a seal leak.

The 90 engine sounds like it was overheated and needs new heads as a minimum and maybe a lot more work that you're not sure about yet.

That all sound about right?

In extreme overheats I have seen the cam bearings melt but in 30 years I only saw that twice.   

In one case a customer fired up a brand new engine, his phone rang, in those days you had to run to the office to answer.   The engine ran till it froze up.  When he came back off his phone call he realized he fired up the brand new engine without filling the radiator.  He was on the phone about 30 minutes.  The brand new Paint on the engine had burned black from heat.   It happens and things get hot and melt.   I have seen new starts without Oil installed also but they stop and lock up much faster.

Most overheats kill the head gaskets first, in many cases that is where the damage stops.  After the overheat with a crushed head gasket you will lose compression in cylinders and get coolant into the chamber or the oil possibly.

If you have pitting on the piston and the missing electrode on the spark plug that cylinder was detonating.  Usually caused by a lean burn/ High Combustion heat.  On modern engines one cylinder being damaged usually means one injector was not working proper.  On the old carb engines one cylinder detonating was either an air leak leaning out that one cylinder or plug wires routed wrong or mis firing, maybe cross firing from one plug wire to another.

Detonation creates huge cylinder pressures and can blow out head gaskets.

Figure that out before starting your new engine or the problem may go from the old engine to the new one.