Steel to Wood Bed Conversion (Installation Questions)

[Rack Man]

I'm getting ready to start my steel to wood bed conversion....I got all new metal parts from Mar-K....So I'm only doing the metal for now....I'll do the actual wood after paint...Before I get started I have couple questions for anyone that might have done it before....

Is it 100% necessary to remove the bed sides in order to get the old floor out and replace the cross sills? ....I am re-using the front bed panel w/the new adapter piece that welds on....so I was hoping to be able to leave the bed sides and front assembled and then simply replace the cross sills one at a time?

Thanks in advance!

Dan