Yeah, the vg30dett will go into an s14, he wants to use the turbos off of it on a vg30e and drop this thing in the s12, since he bought a vg30 crossmember and 5lug conversion plus brake (out of a s12 SE)...
If you have the said crossmember, a complete vg30e with tranny, or at least a bellhousing (since the ca20e uses the same with a diff bellhousing), and are willing to fabricate those headers (you won't have a lot of clearance, but if a vg30dett can fit with both turbos between those suspension towers, I don't see how you couldn't fit the same turbos onto an sohc block in between the same suspension towers), then I'd say go for it... you won't be able to boost a lot if you use the stock piston, but same is true with the ka24... but you can easily make up for it with the 2 extra cyl and 600cc more displacement... plus the VG is very close in weight to a KA, so it won't be a problem handling wise...
if you need to rebuild it, go the extra mile and put some piston in there, you may be able to source stock vg30et piston, which won't be the best thing since sliced bread, but it won't cost a lot and will make a difference. Stock vg30et are able to cope with more boost than a stock ka24 can and they also make more power...