Quick question on 2g crank & girdle install

[Onefast99gsx]

Hey guys-

I'm installing the crank and pistons today finally. I bought all new main bolts. My question is in regards to the head on the bolts themselves because 2 of them are a smaller socket size than the rest. It's been 4 months since I tore this all apart and I forgot. Do those 2 smaller heads go on the rear main end or the front main?

Thanks for any quick help.