Ram you have a similar issue to what i had - although mine was worse as your head looks like a 2wd head but a 23mm version where as mine is the 21.5mm so the holes in mine were even smaller.

I had the head machined to suit which cost next to nothing - the holes were opened up and the seats were machine flat









The nut's that come with proper long studs are hex style as below



I have a spare set of genuine nut's if you get stuck mate