Any head bolt the right length can be converted to an oiler bolt. Just grind a thin slot into the threads about 1/16" wide and slightly deeper than the minor diameter of the thread root. The other method is to drill a small hole dead center into the threaded area of the bolt and drill a hole sideways to intersect with it. You don't need a very big hole- - - -slightly over 1/16" should be plenty, and if it's done correctly the strength of the bolt isn't compromised.
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!