Do you carry the special insert fittings that get installed through a well seal?

Yes, Boshart carries both venturi adapters and venturi elbows. These fittings would be better described as well seal adapters and well seal elbows. They are designed to provide a long shank to go through the well seal. The sweep design of the elbows reduces friction loss and improves pumping efficiency.
PRODUCT # DESCRIPTION
GVA-100-06NL 1" x 6" ZINC PLATED VENTURI / WELL SEAL ADAPTER
GVA-100-10NL 1" x 10" ZINC PLATED VENTURI / WELL SEAL ADAPTER
GVA-125-06NL 1-1/4" x 6" ZINC PLATED VENTURI / WELL SEAL ADAPTER
GVA-125-10NL 1-1/4" x 10" ZINC PLATED VENTURI / WELL SEAL ADAPTER
GVE-100NL 1" ZINC PLATED VENTURI / WELL SEAL ELBOW
GVE-125NL 1-1/4" ZINC PLATED VENTURI / WELL SEAL ELBOW
BVA-100-06 1" x 6" BRONZE VENTURI / WELL SEAL ADAPTER
BVA-100-10 1" x 10" BRONZE VENTURI / WELL SEAL ADAPTER
BVA-125-06 1-1/4" x 6" BRONZE VENTURI / WELL SEAL ADAPTER
BVA-125-10 1-1/4" x 10" BRONZE VENTURI / WELL SEAL ADAPTER
BVE-100 1" BRONZE VENTURI / WELL SEAL ELBOW
BVE-125 1-1/4" BRONZE PLATED VENTURI / WELL SEAL ELBOW