Nic has found this source:

I came across this company for inline fans to be used instead of the squirrel cage style fan used to get air into the cabin.

http://www.detmarcorp.com/index.htm

Items of interest are:
http://www.detmarcorp.com/blowers.htm - can be found on e-bay
http://www.detmarcorp.com/ventscollbxs.htm - can be found on e-bay
http://www.detmarcorp.com/motorwb.htm - for closing up the hole where the steering column passes through.