Very perplexing. I have looked at the engine cast number several times...it is very clean and readable. The "8" digit is definetely an 8, not a 9. I looked at the Pontiac Safari page several times also. They don't have a listing for a 336. Is that because it's a GMC motor? FWIW, Wikipedia states that it was produced by GMC:
336
GMC's own V8 was the 336-cubic-inch (5.5 L) OHV/pushrod engine. It used a 3.875 in (98.4 mm) bore and was produced only in 1958 and 1959.
While both the '58 and '59 GMC V8 engines were advertised as 336-cubic-inch (5.5 L), the '58 version was based on the Pontiac 370-cubic-inch (6.1 L), but with a smaller 3.875-inch bore giving 336.1 cubic inches (5,508 cc). The '59 version was based on Pontiac's 389-cubic-inch (6.4 L), but with a smaller 3.78-inch bore giving 336.9 cubic inches (5,521 cc).
