There's another thread about this here:
The Plymouth Weslake DOHC Motor from the 60's
Was up on ebay for a mere $161,499.95 a while back:
eBay Find: Weslake Rod Shop '69 Dodge 318 V8 Indy Engine - EngineLabs
re: the distributor, the Gurney Weslake Fords had the same setup - I'm betting it was done for Indy-type cars, where you don't want things sticking up in the airflow (less drag) - they mounted them with all the 'front end' stuff in the back on the Indy cars.