stripped starter bolt

i've got a 69 2a which has a stripped thread on the started motor lower bolt hole in the bellhousing.
what thread can i tap to fix this, any ideas?

you'd be better getting the right size thread insert otherwise when you drill the starter hole to fit yer new bolt you'll not be left with much metal, then you'll be risking a cracked starter. which when you replace it you'll find the same problem. as fer the size ah reckon it will be abart 3/8 unc or possible unf .