You will need 69-specific bb frame brackets. 67-68s are designed for the non-interlock mount. The brackets offset the engine about 1" to the right; you will also need the bb manual trans crossmember. You can re-drill the one you have. The heater core is different and mounts with the hoses to the left requiring modifications to the cover. The z-bar or cross-shaft is about 5/8" longer than sb and is repo.
Also different for bb is the radiator, shroud & bracket, shifter mounting plate and rods, male throttle link, oil pressure line, power brake hose, battery cables.