What temp Tstat are you running? Is that a stock five liter? My 93 cobra liked a 180 degree instead of the 192 degree that came from the factory.
*edit - I see you have the GT-40 heads and 306ci. What do you have the timing set at? No mechanical fan? Do you have an electric setup? That radiator should be adequate if you have some type of fan unless you're running under drive pulleys.
It has a 180* t-stat but it also has under drive pulleys. It has no mechanical fan but it does have the stock electric BMW pusher A/C fan. Timing is pretty conservative now.
I will either see if i can fit a mechanical fan in and if not i will likely get a good puller fan and shroud. The AC will also add some temp to everything so i may just shoot for overkill and not have to worry about it.
iI never woulda thought to go this route... pretty sweet, I have the same e30 in stock for mostly... I will prolly end up going the typical S50 route like many others though. Def want to see more video of fun in this thing!