Here is some pictures of the Mark IV 990 BBC LS6/&7 heads I picked up today. First few photos show a Gen VI 454 truck head for comparison:

990 chamber.jpg990 exhaust.jpg990 intake.jpg

I couldn't easily pull a red-black carby 308/304 head out for comparison but I had some old VN heads that I stuck next to them. You can swee how they dwarf the VN ports.

990 VN exhaust.jpg990 VN inlet.jpg

The heads look like they have been de-shrouded around the valves a little and they appear to have been cc'd at 134cc. Stock ones are claimed 118cc which will mean compression with the TRW replica 1969 L88/ZL1 piston drops from around 12-12.5:1 to about 10.5-11:1 which given I have an L72 cam rather than an L88 cam will probably be better anyway, at least it has a chance of running on 98 or 100 octane fuel.