It would also help to know the type of Chevy crate that was installed. Small block, LSx, pre-Northstar?
Not saying you are ignorant, but here is a rundown on firing orders-
GM small block V8 engines are 1-8-4-3-6-5-7-2.
GM LS V8 engines are 1-8-7-2-6-5-4-3
Its also important to note that the cylinder numbers alternate starting from the left side of the vehicle as pictured below. This is true of all GM engines EXCEPT Northstar and some Pre-Northstar engines which are opposite.
(photo from CraigBlock)