i have the old style bravo 1 (1988) without the external fluid reservoir i just purchased a 1995 bravo 1 new style transom assembly which has the reservior connected to it. and also has the plunger that goes into the lower unit..

will my old style lower unit bolt on to the transom assembly without having to do anything to that plunger or will i need to remove it and block it off somehow? or will it even work with the old lower unit thanks in advance

Just take it out. Your gear lube can't leak from the drive if there isn't even a hole in it. I can't even remember Bravos without the gear lube resevoir.