Thread a piece of stiff wire like an acetylene welding rod through the old line to act as a guide to get the new one through the water jacket. Be sure to leave plenty of extra length at both ends to allow for gradual bends before soldering the line to the "through the block" fittings, and DO NOT use steel brake line- - - - -only 3/16" OD copper tubing. Steel line will rust out from exposure to the coolant. Good luck!
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!