need help with screw size

Hi guys I`am starting my first detailed bike a hayabusa from Tamiya just going to replace the bolts with metal ones for my first attempt might buy some p.e parts if I can find some. I just want to know how you guys find the size of bolts for your builds inparticular the size of the fairing bolts also engine bolts.

sorry posted in wrong section

A few links I have. . .

http://www.scalehardware.com/

http://www.am-works.com/lw35025-bolt-heads-various-hexagonal/

http://www.scalemotorsport.com/nuts-bolts-washers-duzs-fasteners-photoetch-set.html

Look at Top Studio TD23020 otherwise I usually dremel the screw head to a smaller size and then glue a PE bolt on top

ok thanks for the advise i might get the dremel out and have a go.