See the “1969 150J Spinner Replacement Options” posted on “Tech Questions” on 07/16/2017.
The rear bulkhead, # 0450040-1, fits 150 F, G, H, J, K, and a used one is hard to find in good condition. The new price is advertised at $850 - $1200. You may find one on eBay for $380 - $475, but beware: Used bulkheads may have cracks or be work hardened.
Univair sells a new PMA model for $338 + shipping. The Univair backing plate, U0450040-1, is in stock, very well made and probably better than the original. If your mechanic can get a discount from Univair you will get your best deal.
