okay from what i remember the shelf the the engine seal sits on, is two pieces welded at the back edge. i want to cut it out for air flow reasons ( radiator ), is it welded at the firewall or should i weld it after i cut it. there is a great pic of joe's 914rs ( stole pic below ) where he cut out the shelf.

It is at a seam between 2 different parts of the firewall. If there were no engine shelf there would still be a lip. The shelf is spotwelded to that. If you cut at the right place you will only have to cut 1 layer of metal.. go too far towards the firewall and you'll have to cut three. If you go wayy too far towards the firewall, your car may fall apart.