I don't have an A so I can't tell you much about distance from the waterpump to the radiator. But since you are planning on using an electric I can tell you that the new units from Cooling Components (fan and shroud) are less than 2 3/4 inches thick. Althought not necessary it would be good to leave another 3-4 inches behind the fan to allow for clearance and maintenance to the water pump. But I suppose you could actually have less than 1 inch clearance between the two if the need would be there.

There are several members here who have A bone's that can help you with more precise measurements.

BTW, welcome to CHR and when you get a chance how about posting some pix of your project or any other rides you might have. We love pictures.