The 153 tooth manual flywheel can be used on 194, 230, 250 6 cyl as well as 267, 283, 305, 307, 327, 350 small blocks (prior to 1986) and 396, 427 big blocks. Lots of interchange there, no problem. As you are finding though, you either need to buy the 3849309 bellhousing or have your's machined to the larger opening for your Saginaw.
Do you have all the clutch pedals, linkage etc? If not,the best thing to do is find a complete 64-67 Nova or Acadian with a manual trans (has correct 309 bellhousing) and take everything from it. The one snag is the clutch pedal needs to be 66 or older for your car.
Carl (in the prairies...)
65 Canso Sport Deluxe (Sold)
67 SS 327 (Sold)