Here's what you can find on Wikipedia.com:
N H Buchanan Motor Co Pty Ltd was an Australian kit car manufacturer. It made sports cars in the 1950s.
The original body produced by Buchanan was a fibreglass item based on an Aston Martin DB3-S racing car. Buchanan borrowed a DB3-S and pulled moulds from it while it was in Australia. The styling was altered by filling in the scallops either side of the bonnet and reshaping the grille opening to be oval. Because the target market was for rebodying of early model MGs, the Buchanan moulds were cut and extended between the door openings and the rear wheelarches, adding several centimetres to the body length.
Racing car kits were also produced, consisting of this type of body plus a fabricated X-frame racing chassis manufactured from steel channel sections welded face to face to form box sections. The chassis used mechanicals from an FJ Holden, with the front suspension crossmember and rear axle assembly being shortened to suit the narrower body.
The second model, the Buchanan Cobra was introduced in 1958 as a production vehicle based on Standard 10 mechanicals. Only 7 were manufactured.
Buchanans were used on the road, but also raced quite successfully. You can see some of the cars pictured on the side. (pictures taken from "Buchanan Motor Company")
To some extent Buchanan can be compared with Devin or JWF. I like this breed of course and wouldn't mind owning a Buchanan.