You will have to weld up your spyder gears in whatever trans you use.Weld an old bus cv outer to the output shaft on the trans and thread it to 3/8 coarse threads.(You don't have to do this flange if you use any vw because they have a bus flange.)Run a stock bus shaft back to the same set up on a Lincoln Continental irs diff.Then the same type set up with the Porshe axles going out to your 3x3 trailing arms. The irs diff will be mounted exacly where your bus diff would have been in a traditional buggy.You will basically have a diff going into another diff making an incredible final drive.Use 1st gear on slow rock crawling, 2nd gear will roast my 38's.My vw trans is a 5 speed so 5th gear will go down the road easily at 65 mph.The Lincoln irs I have is a 327:1.So my 339:1 Passat ring n pinion is multiplying a little over 3 times. The vw trans come in over a dozen ratios and the Lincoln comes in 3 or 4, so look at the many gear combinations you can use.I've tried and busted many other maker's irs's but the Lincoln teeth are MASSIVE and so far UNBRAEKABLE.Oh and the lincoln diff has to be mounted upside down to make the rotation go forward. The gear shifter on a manual vw trans is 2 cables and a shifter . All you have to do is bolt the whole shifter to the floor and you are done.Same with an automatic.NOT putting anyone down!,but with this set up you don't need Kennedy adapter plate ,lg clutch ,lg pressure plate, lg flywheel,lg starter, slave cylinder etc.Loves 87 octane gas.No high dollar trans, no 4 spyder diff.I can introduce sliced bread and people will still want to break it off in chunks.I'll be glad to walk you thru it if you go this route Thanks.Oh, I did not have the extra room behind my seat like you do so I had to make longer trailing arms. They work but I seen an air bag set up and was impressed.So I'll make a looong 3x12trailing arm with air bags this winter.
Oh. A retired vw dealer friend of mine said he'd rather go with a lighter power to weight ratio 1.8 150hp turbo.Just an idea. Go Honda Nissan whatever if you'd like. Better parts availability.