you can find top dead center with a positive stop screwed in a spark hole. rotate it till it stops then back till it stops and mark half way between. i for one would not want to weld a new tab on the timing gear cover with it on the engine. an out of position weld with no room is good for a burn thru! the easy way might be to change the timing gear cover to one with a timing tab. you could use the positive stop method and a degree wheel to mark new marks. you can even mark your balancer and use any fixed point as position. but like everyone said vacumn gage will get you there.
