Cosworth head gasket

I've ordered my cosworth head gasket but am wondering if I've ordered the wrong one. I've gone for a 87mm as that's all that was listed but I'm using 86mm pistons. Now I've checked a 87mm headgasket on a old block up the garage & the gap around the cylinder seems minimal.
Will this be ok?

I would say yes 87mm is the bore size not the pistons but it will sqwash down to big a gap leaves exposed area on the block which will heat up but as long as when fitted there is no over hang  to pistons which will also create heat should be fine i would say. 

Big gap no 
Close ok 
Overhang no   
Someone might confirm this better be carefull when you bore dowl holes to get them even as not to pull the gasket over

Any thoughts lenny ?

I've had another look today & the gap is very minimal. Also found a invoice from my old engine using a cossie head gasket 87mm with 86mm pistons so think its fine

that will be fine to use james
just open up dowel holes and will be fine

the hks ones are 88mm which will leave a big step between block and combustion chamber on head, this can then become a major heat spot which could destroy the head and block if your using 86-86.5mm pistons

thanks bob. thats good. i will be in touch shortly..