The only 261's that I'm aware of that are capable of running hydraulic lifters were Pontiac engines sold in Canada. It might be possible for a very well-equipped machine shop to gun-drill a 261 truck block for a hydraulic lifter oil gallery, but given the current status of "machinists" these days, finding a shop willing to attempt that procedure is a little less likely than encountering a chicken with lips!
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!