I don't think it will, i'm rebuiling an 84 dohc supra engine right now at school, but the holidays are here so no work is being done on it. I don't think it will bolt up, but the hemi combustion chambers with a crossflow design dohc would be sweet.
I have never tried to fit a supra head and I wouldnt waste my time on it. Sure it is an excellent head with the 4 valves, centered spark plug, cross flow, dohc but there are LOTS of factors to consider for it to be possible.
Let me make a short list.
1. Cilinder center to cilinder center distance - it cannot be close to equal, it HAS to be exactly equal, something that i really really doubt.
2. Oil passages to the cam towers there are just one or two places that the oil passes from the block to the head in the L28 block, they would have to match the supra head.
3. Distribution chain geometry - sure you could get a chain any length but what about the guides, the tensioners and the gears?
4. The gears - you will use one of the two chains (supra or nissan) so all gears would have to match.
5. Water passages - they have to coordinate
6. Gasket - decisions decisions.....which gasket to use? supra or nissan?
7. Head bolts? fine, and you?
I think I can come up with about 3-4 more issues if those are not enough.
So if you want a cross flow, twin cam nissan engine get a RD26 from a skyline or contact OS Giken in Japan for the twin cam head for the L28 which I dont thing is available, and if so, it should cost more than $5k.
Why not put the supra 6er into a z? I know they blow head gaskets left right and center, and the local z club would have assassins on your tail 24-7, but it would be a good engine, definately faster (heavier???). Supras are decent fast and they are classed with the other panzers like mustangs and camaros for weight. And it should'nt be taboo anyways, there are a few well respected rotary Z's out there.... But then again 5.7 chevs are easy to come by.