1969 1/2 ton panel truck restoration info needed

[chris mc bride]

I have a 1969 panel truck.It was bought new by grandfather.He sold it to guy in 1978 and bought it back for 1/2 the price in 1995.The guy had let it run down and get some rust issues that I am working on now.It came originally with 396.I
Im looking for some production number on this truck.I know there where 5492 produced according to this site.I would like to see how many had big blocks.Im looking for matching number block to rebuild as part of restoration.It now has 454 that was installed new in 1976,Ive since rebuoilt the 454 its in great shape,I just want the matching numbers figuring it can only add to value.
If anyone know where I can find more info on this as panels seem to be the red stap child of chevy truck.Maybe its just they are rare(oh well) that makes finding parts and info so damn hard.
Also wondering how much making some interrior up grades will hurt resale value.Im planning on more modern interrior and a auto matic trans like 700r4.I figure either will be easy to convert back as I will not be cutting or altering the body,floor pan or the chassis in anyway.
So anyone with input let me know.