Walter;

Your SU Fuelbowls are vented to atmosphere, so they dry out when car is parked for a long time...prolonged cranking is often necessary to get fuel up to the bowls again if pump prime is OK...but sometimes, prime of the Fuelpump is lost also, so no amount of cranking will help...this is not necessarily a failed fuelpump!...I'd recommend blowing some exhale pressure into Tank filler as a helper monitors for fuel coming from Fuelpump outlet. When is does, reconnect to carbs, but prime Fuelbowls manually (and spray some carb cleaner into Bowl-valves to flush them, see below) so you can start immediately.

After start, monitor fuel bowls for overflowing...they like to overflow at first start after prolonged parking, caused by the gum fuel left behind in bowl-valves. See also: http://www.sw-em.com/SU%20Carb%20Service.htm#Inspection_of_Fuelbowl_Lids,Floats,and_Bowlvalves

Cheers