Thanks to Dave, I won't have to hack the Datsun and MG manifolds! All the way from Australia, a perfectly fitting manifold to mount my MG SU carburetors to.

Through research, I found that it's a Triumph manifold with, I believe, H4S carburetors. I was able to find that the port holes are the same as my A12 (approximately 1 inch) but I couldn't find what the distance was between the holes. If it's close, this is the route I'll take.
Any Triumph experts?

Tell me if I'm wrong but it looks like this would fit...

Whalebone-dave: it would be great if you could post a picture. I would be very interested if it's what I'm looking for.

I actually have been using that same picture of the homemade manifold for reference! Yes, HS2 is a vertical pattern but my head is round port. Looks like I'll be building my own.

Honestly, I know nothing about the Datsun SU manifold but if my (British) HS2 SU carburetors will bolt up to it, somebody please let me know before I cut up my Datsun and my MG manifolds!

I can't use the manifold from Carburetors.com because it is for HS4 SU carburetors; I'll be using HS2.

To smellsofbikes: the engine fits pretty well but there is not enough room for an engine mounted fan, you'll have to fabricate new engine mounts and adjust the length of the driveshaft.

Looks like I have an early A12 with the distributor under the #1 spark plug. Any suggestions for parts suppliers?

OK, why can I not post pictures from my computer? I'll click upload and it will load for about 3 minutes then stop loading as if I hadn't even tried to upload a picture. The pictures I posted are from my other thread.

Instead of filling up the forum with a million separate questions, I decided to start a thread (which I also find to be more interesting to the people who know more than I do and, in turn, tend to be more responsive).

Here it goes, I have an A12 engine and transmission in my 1964 MG Midget that I am currently restoring (here is the thread on the restoration 1964 MG Restoration). I know next to nothing about Datsuns which is why I have come here.

I ran a compression test (mildly warm) which returned: 125, 115, 115, 112. Probably need rings.
What other areas should I be checking for wear? (end play and such?)
I'm going to install a complete clutch kit: PP, disk, through out bearing. How hard is it to install a new main transmission seal and rear engine seal?
As if jumping into a completely unfamiliar engine wasn't enough, I plan on having the manifold modified to accept two British SU carburetors. Wish me luck...