need to know specification differences on the 390 cid 2v , 4v & 6v big blocks.any information of a web site or personal knowledge would be totaly appreciated

Any particular year? There are lots of different combo's over different years.

sory for taking so long to reply 'EFI Guru'.had to wait for engine seller to be home to read compliance plate.anyways.it is out of a ford galaxie 500, build date 14/1/65 with a c4 auto but currently has an fmx bolted to it.also came with spare set of supposed 6v heads,factory 2 x 4-barrel alloy manifold with matching no. carbies.was told by original 1 and only owner that it currentl has the single 4-barrel manifold , carby and 4v heads off his old 66 model 390 galaxie [that he wrote off 10 years ago] because he kept stripping the guts out of autos all the time , and that he was getting to old for that kind of crap ,and the price of fuel etc .which is why he fitted a 302 efi motor to it.probably too much information but i hope it will help. thanks.

No wuckers 'fordmods newbie',
Ok a '65 390 head has 73cc chambers and 2.02 and 1.55 valves.
6V(and 4V)heads are basically low-riser heads(refers to inlet port height) and had slightly taller ports than the stock 390 head (2.34" vs 2.24") but the same 1.34" width. Depending on year 6V & 4V heads can have 67,63 or 65 cc chambers and either 1.55 or 1.66 exhaust valves. Do you have any casting numbers off these heads?
FE's never had C4's originally fitted. The FMX was likely what was originally fitted...later FE's got the C6.