Also check the walbro site. They list all their carbs and the specs. IT is tedious to search through.

This may help, here is the list of Wt carbs with accelorator pumps, and hi and low needles and no primers. I compiled this from other's work and take no credit. It at least tell you the venturi size on the most desireable carbs. I am sure there are more.

6.5 mm with fuel pump return spring (4 stroke)
WT 366-1
WT 456-1

7.95mm
WT 37-1
WT 424-1

9.53mm

WT 35-1
WT 38-1
WT 204-1
WT 357-1
WT 367-1
WT 381-1
WT 385-1
WT 417-1
WT 449-1
WT 450-1

11.11 mm
WT 29-1
WT 356-1
WT 358-1
WT 464-1
WT 516-1
WT 517-1
WT 527-1
WT 613-1

12.7 mm
Wt 513-1
Wt 537-1

13.49mm
Wt 171-1
Wt 172-1
Wt 228-1
Wt 285-1
WT 529-1
Wt 451-1
Wt 480-1
Wt 540-1
Wt 542-1
Wt 555-1
Wt 610-1