don't know if you solved the issue with the head gaskets already, I've got a 3.5 V6 Savali as well, all in pieces but ready for assembly.
Got it from a friend who purchased the engine to fit his HAWK Stratos Replica but the HAWK was sold last year without this engine.
Through a friend who does mainly US cars / engines he got some new specially made head gaskets for a reasonalbe price (71 USD a piece, left and right bank).
I just checked out the gaskets, they are 1.5 mm thick (base layer) the cylinder rings slightly thicker, which is the same as for the old 3.5 gasket (I have one as well).
3 liter gaskets are slightly thicker, 1.8 mm for the base layer and 2.1 mm for the cylinder rings (I got a new set of these as well).
The US gasket supplier (Cometic) used 1.5 mm Reinz base material for the gasket and look OK, only the copper seals for the oil channel are missing and now rubber seal all round is applied but this seems to be not to much of an issue.
If you want I can find out the contact.