Thanks for the reply's everyone.
This is a budget track car,so throttle bodies/management/yb etc. are a bit out of price range,plus i want to keep it simple with a standard engine that gives good power on carbs,and is easily bolted in the car,and easily replaced if it blows up.
I think i'll go for the I4,as this gives more power as a standard engine,and i have a 1.8 blacktop zetec in my garage that just needs 8 new valves,so i can always change my mind in the future if the I4 doesn't fit in my bubble arched mk1 shell that will be ready soon.
One of them will be at croft for sure though