Race: Other engines for the NC29 chassis?

The "From Road rashed to race" Blog entry very quickly got a bit out of hand so I have removed some detail and made it more of a story. The real bones of any particular job, such as this one, are now in separate blogs which I will link between whenever relevant. This should make it easier to find useful info whilst still getting it all down.

Seeing as I had the engine out of the bike during my initial strip down, it seemed like a good idea to drag out one of the spare engines I had bought to see what the differences were and if they would fit in the NC29 chassis as the forums seemed to suggest.
I had a choice of an NC23 motor which would need different carbs due to different inlet port spacing or another NC23 motor with NC29 heads which seemed okay for a straight swap should I decide to go down that root.
I picked the NC29 head/NC23 case' hybrid as this should be most similar to play spot the difference.

Turns out quite a lot. 
Engine mounts are different in levels and spacing, cooling design, mountings for the thermostat, separate barrel from cases, wiring and god knows what else.

That's not to say it wont fit, just more of a pain. Maybe now would be a good time to read up on this thing. Incidentally both engines have breaker writing all over them. They at least have that in common.

NC23 Left NC29 Right

I had a quick inventory check and I had engine numbers:
NC23E102XXXX
NC23E12XXXXX
NC23E13XXXXX
NC23E13XXXXX (might as well include the road bike in this investigation)

A bit of google searching brought up a couple of sources with engine numbers for CBR400RR's such as this abbreviated info from Fireblade.org:
CBR400RR-J (1988) NC23E-1020001 to 1036510
CBR400RR-K (1989) NC23E-1090001 to 1098123
CBR400RR-L (1990 and 1991) NC23E-1300001 to 1310636
CBR400RR-N (1992 and 1993) NC23E-1420001 on
CBR400RR-R (1994 - on) NC23E-1500001 on

So I had one CBR400RR-J NC23 engine, two CBR400RRL NC29 engines and one, oh hang on what is that?
I couldn't find reference to the NC23E12XXXXX anywhere. 
For a while I harboured a small hope it was some "experimental" pre-production NC29 engine that had found its way into the open market, it wasn't. I ended up going down a deep rabbit hole looking at every four cylinder 400 Honda had made till I started to recognise the shape of it as a Honda CB400 CB-1 motor. a check up on a VIN database confirmed my suspicions so now I knew that my supposed NC23 engine was in fact a CB-1 engine! Well that would explain the odd case on the engine you can see above which the previous owner had clearly swapped at some pint. At least I knew that bit was interchangeable.
Well enough of that, lets see it it will fit.
 In short, it doesn't.
The rear upper mount is too long leaving the engine too far forward when mounted and also leaves the lower mount swinging in the breeze. Even if you didn't use the upper mount as it should (maybe use brackets?) and slide it further back; it hits the water tank before the engine is far enough back.
To make this fit you would need to chop off the upper mount and reattach it in a more vertical position like the NC29 engine. Even then I am not sure it would be that simple.
There is no aft barrel mount as the NC23 uses a head mount instead. I guess you could just use the forward barrel mount along with the two rears after modification?
Basically I am not going to say that fitting an NC23 engine is impossible but neither is fitting a gas turbine engine. I could see a swap working the other way more easily but I am calling bullshit on an NC23 engine being a drop in on an NC29!
You can actually see on the NC29 engine where there is a blank to allow the cylinder head chassis mount could be drilled and tapped. Which is what has been done to the hybrid engine.

NC23 engine left NC29 engine front. They suddenly look very different.

After a fair break from this job which was already getting a bit confusing I decided to step back into it.
I was now looking at building a good engine. I was clearly going to use the NC29 cases but was now toying with the idea of whether the crank could be used out of one of the spares. I mean the timing cover fits right?
The main thing driving me here was that the crank webs appeared to have been machined on the race engine which would save me the expense of getting mine balanced.

The crank part numbers according to CMSNL are:
NC23 - 13300KY2000
NC29 - 13300MV4000

Part number differences aside, the exploded diagrams look slightly different in their webs, the dam drive gear is wider and the pistons are very different in design. This doesn't mean it will not fit but equally doesn't make me want to go breaking into a serviceable engine and pulling its crank out on the off chance.
I instead decided to buy a new crank and just rebuild the engine I have. I will link to this seperate blog entry when it is done.
For now this concludes my foray into looking at engine transplanting. It's as dud as far as I am concerned. Does anyone want an NC23 engine?