bottom bracket advice

Hello I need some BB advice. i hope someone can help

I'm replacing the complete chainset (triple)& cassette on a friend's
Gary fisher. Aquila from the 1990's

Keeping an 8 speed as I don't want to change the shifters.

The shell size is 73mm.

i'm intending to fit an 8 Deore splined triple (spare part)

my question is:

What size spindle should I use ?

will a 113 be ok as the down tube diameter is 35mm.. or go for 118 and
risk a v wide Q factor?

i cant take the bike apart as he's still using it! even though i've
warned him not to.

yours