Search Ebay for "GMC 270 timing gear". There is an auction showing a slightly rusty new old stock crankshaft gear with the timing mark visible. Also, check your PM's. I can walk you through a method of timing a cam with no marks at all, but it will take a phone call to do that.

Edit:
The same timing gear also fits a Chevy 216/235/261.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!