OK I got no answers to my worries over the cracks round the outside of some fixing holes thread so I went ahead anyway with fitting it.
I am using the so called 8v baffle plate which has a moulded on slightly ribbed rubber gasket 90528632 @ £18:90 from Autovaux. (gen GM)
I elected to clean up all the M6 holes in the block first and was glad I did, each one had lots of black rtv and locking fluid leftovers down the blind holes. I ran a tap down each hole and near each one had around half the holes depth filled with rtv which got trapped in the taps flutes and came out leaving nice clean holes. Had I not done this I am sure some bolts would have bottomed out before tightening the sump down right.
As I was doing this with the engine on the crane hanging sideways I fitted 2 bits of M6 studding on opposing sides of the block, rtv'd the baffle top side and slid it up the studding so it was held in the correct place against the block.
Fitted the oil pick up with new o ring and locktited the bolts home.
Then rtv'd the base of the baffle and slid the sump up the studding till it too was in place.
I used M6x20mm long stainless cap head screws with washers (just the right length) and locktited them in place, the front 2 oil pump fixings needed M6x25 long to use all the available thread in the alloy.
I think you could get away with the original M6x22 bolts but only if the holes are cleared first, in my block they would certainly have bottomed out before tightening the sump.
This is the new baffle plate.