Here's how I installed this transmission. Keep in mind that when I started, I was told it wouldn't fit and therefor the modifications might be a bit unconventional. You will have to do a little welding and some cutting, however not to the car. I will list the parts needed at the end, so here we go.
If you have the transmission, take a piece of cardboard and make a template of the bellhousing, be as accurate as possible. Take your template and engine plate to a machine shop. They will have to weld some steel and have them match the template to your plate drilling 3/8" holes (Not Threaded) Have your flywheel re-drilled to accept a Datsun 280ZX Clutch and Pressure Plate. While this is being done, measure back an inch and a half inside the bellhousing and mark with a magic marker. Make a line all the way around. This is where you will have to do a little grinding.
Use a grinder with a 80 grit flap disc. Grind out any humps, make it nice and smooth all the way around. Where the starter bolts on this trans will have to be grind down. You need to have a thirteen inch diameter at all points around and an inch and a half back inside the bellhousing. (Don't worry about where the starter bolts, your not going to need them anyway). When the engine plate comes back, bolt it to the bellhousing using 3/8x21/2 inch bolts. You are going to use your starter so mark the bellhousing and cut out where the nose of the starter will go. Start out small and keep fitting the starter until you can bolt the starter to the plate with the plate bolted to the transmission. If you take your time you can get a really tight fit and you can seal it with silicone. Remove the pilot bushing from your engine and take the one from your clutch kit to a machine shop and have them make one that about an inch and seven eights long (the MG bushing is an inch and a half) When you install the pilot bushing, make it even with the cup on the crankshaft. You will see what I mean when you install it.
Now you can start putting everything back together. The plate, the flywheel, the clutch assembly, and fit the trans. Bolt together with the 2 1/2 inch bolts. You can bolt the starter in place. Use a nut and bolt for the top bolt. You can use the original bolt for the bottom as it is threaded. You can now install the engine back in the car. Here's where it gets a little tricky.
The shifter of this trans is going to be 3 inches back from the MG shifter, which puts it under the tunnel. Now is the time to modify the shifter. Pick up some shifter parts from the junk yard to use. I have a picture of what my shifter looks like. Cut the Nissan shifter and weld a tab to bolt your shifter to. It has to come forward and up, also to the left as the MG shifter is offset. When all is finished you may have to open the hole in the floor for fifth and reverse, but nothing major. Once you get that fitted you will be ready to install the crossmember.
You will have cut the cradle off the crossmember, (get one from a junk yard if you don't want to cut yours) and weld a piece of steel an the back edge with a slotted hole. (see photo). Drill two holes in the trans mount just to the rear of the rear orignal holes and mount to the crossmember. Install your shifter before you jack up the trans and secure in place.
As for the slave cylinder hose: To make it easier, you will have to cut the end off the steel clutch line and replace it with a 1/4 inch inverted flare (7/16-24 nut) and have a hose made with a 10mm end on the slave cylinder side and a 1/4 inch female inverted flare end approx 14 inches long. You will need to have a driveshaft made using the front yoke of the Nissan shaft and the rear yoke of the MG shaft. I am still working on the speedo cable and will post it when I get it made up. I want to emphasize you will doing all the work and thinking, there isn't a kit to make this work and that's why I was able to do this for so little. I've spent many hours trying to figure out things and you will have to do the same. I guess that's why those kits are so expensive.
Parts needed: Nissan 300ZX Transmission
Clutch assembly: Datsun 280ZX
Transmission Mount: Early Chevrolet
Bolts: 3/8 x 2-1/2 inch
Basically everything else has to be made or modified.
I hope this helps and if someone wants to add suggestions or comments, that would be great.
I will be glad to answer any questions and help in any way. I would like other people to enjoy working on their cars and saving money. I know it sounds complicated, but it can be done with a little patients a little thinking and a little problem solving. Try and find a machine shop that will work with you. They can become your best friend.