Redline have these inlet manifolds availble:
PART NO. 12-22 Toyota Twin Cam Engine 100KW 1600 4AGE Single port. Manifold designed to accept 2 x 45DCOE Weber Carburettors.
LINKAGE KIT P/NO.42-2500
PART NO. 12-23 Toyota Twin Cam Engine 89KW 1600, 4AGE Large Twin Port (TV15). Manifold designed to accept 2 x 45 DCOE Weber Carburettors
LINKAGE KIT P/NO.42-2500
that is about everything you will get off the shelf. none of these manifolds are to suit downdraught, so you're all but out of luck.
