preppeing chassis for galvanising

Hello all

I'm in the middle of doing a project with my uncle for is series 1 88"

He has asked and insisted that the chassis be galvanised.

My question in in regards to drilling the chassis in prep for it being dipped,

What size drill holes are best / required and how many and where about's are they required on the chassis?

I would have thought the chassis would have enough standard holes already in them....wiring holes, drain holes and such. I would be more concerned about how you remove rust from the inside of the chassis. I suspect acid dip will deal with this to an extent but I suppose it depends how bad it is inside?