i have heard of performance converters with 6 holes. they are all 6 supposed to be used. there is probably a performance flexplate to go with it, although i think drilling new holes in the old fexplate is acceptable also.

i dont know enough about it really. i would maybe try to get him to take it back and give you a regular one. perhaps it would be cheaper too. or at least ask him some more questions about it.

there is the possibility it is a universal converter, to fit more than one flexplate, but i have never heard of that. i wouldn't want to use only half the holes, with the other half touching the plate and not bolted to it. dont know why... it just doesnt seem right. i'd rather machine in some more holes for it.

stock converter is probably in the 1800 rpm stall range. i dont know of any way to check it. you want to stick with that unless you have a low rear gear (high number) and a hot cam... or so i have read.

try to find out who makes it, and do some research through them, and the guy who you got it from. maybe it's worth drilling the holes.