The reason you start with bell housing is starter engagement to the flywheel diameter. A stock 69 RR with 383 would have had the 69 bellhousing and the 143 tooth flywheel. If that bellhousing is correct for 69 or even 68, then you get the 143 tooth, turn them over and post a picture of back side. Internally balance 69 383 motor would have a fw without extra large holes partially drilled to compensate for an externally balanced motor.