Technical BOP trans. adapt, safe to grind on the block??

Have a bunch of sbc's
Got 4 BOP transmissions (3 350, 1 400)
Thought using a BOP trans to sbc adaptor might open up some possibilities for me...
Looked at a bunch of commercially available ones - they range in thickness from 1/8" to I think a 1/4"
Cut one of 1/8" cause I had the material on hand and I thought the thinner material would easier to get torque converter spacing right.
If any of you have experience with these you know what I am talking about...there is a bellhousing bolt in the BOP bellhousing that doensn't have a matching hole on the SBC (think the space on the back of the block where you would see 3970010). The thicker adaptors use a threade hole in the spacer and countersunk fastener on the trans. side - the thinner ones look to have a bolt/threaded flatstock on the engine side - it would appear you would have to grind some clearnance on the block to make room?? Is it safe to do a small amount of grinding on the "bellhousing web??" on the block? My thought right now is if I were to weld a button head fastener on the enginc side of the adaptor I could grind a little clearance on the block so it fit flush up against the back of the block?? This would be used on street engines - no real high power race type situation?
Any thoughts??? Thanks

 

The Adapter that I still might have out in the shed has nuts welded to it in the couple of spots where the BOP bellhousing doesn't match up to the Chevy pattern.

It looks like the joe cheap one comes with 4 bolts and lock nuts.

The Transdapt one that is thicker is counter sunk for the two holes in the Chevy block that are behind blind spots in the BOP bellhousing plus bolts and nuts to complete the job.
That one still doesn't come withe spacer dor the converter snout.

 

Converter snout is an area I'm still not clear on...
The way I understand it is to fully seat the converter on the input shaft then slide it towards the engine 1/8" to 3/16", thus then maybe needed some spacers/washers to mate the converter to the flexplate?? Is there supposed to be a spacer to span the gap from the converter snout to the flexplate?? Thanks for the info.!