"can i put a camshaft for a 1988-1995 engine in a flat hyd. engine from 1984?"
If I'm not mistaken the cam you have has a nose machined with a step to fit into a timing chain sprocket specifically made for roller cam blocks(1985-93 or so).
I'm pretty sure you'll have to buy a timing chain set for an '85-'93 engine and buy the cam retainer and modify it by grinding off the mounting tang/ears and using whats left as a spacer between the timing gear and cam to keep the cam from sliding into the block too far and contacting the rear cam tunnel plug as well as cam lobes hitting the wrong lifters.
The retainer is used on stock roller cam engines and keeps the cam from moving fore and aft in the block. Flat tappet cams have the lobes ground with an incline/slope that makes the cam try to move to the rear of the block constantly only the timing gear stops it.