Insulation, Radiant and Vapor Barriers - House Wrap and Sheathing over Old House

I'm a new homeowner and have a couple of related questions. I have a late 1800's single family home with asphalt siding over the clapboards (probably done in the 50's). Chunks of the asphalt are missing and I have to re-side. I've debated tearing down right to the wood sheathing to get an even surface. Is there a benefit that outweighs the time involved in removing both layers of siding? Will the house be better protected / insulated? I have blown in insulation (very old) and holes all over the house. I've had different people tell me to side over the clapboards with furing strips. I'm worried about the spaces between the old and new siding, and what may turn out to be an uneven siding job.

Thanks for your advice,

Ian

I would tear it off and put Tyveck vapor barrier on. When I remodeled my own house I found two layers of old siding under the top layer. Why screw the next guy. But this my own opinion.

Good point. Thanks for the advice!