My roadbike 105 BB ht II has died, can i swoop an slx bb HT II over, -i noticed that the height was not the same…. but i have one spacer, that i could add ???
will i die and fry, trying ?

shimano road bbs are shorter than mtb. i believe slx are longer than standard mtb again. worst that can happen is that you run out of thread in your bb shell and you don't bottom the cups/spacers out against the shell.
if you pushed it you could probably furr up the thread on the slx cups. getting them back out would probably cut them again, assuming a steel frame, or it could get galled up but probably recoverable ok, but if ally you could get into trouble..
why not just fit road cups? cheaper.

Open both up, swap the bearings, Bob's your uncle.