I assume you do in fact mean the AC fan, not the heater blower (which is the topic of this thread). I have replaced my AC fan with a 60's vintage Ford Mustang if memory serves me correctly. Same exact motor except for price. It blows the same as the original. What I have done to improve performance is:
- sealed all gaps/holes in the AC duct with the good foil duct sealant tape .... better airflow
- converted to R-134
- removed the original condenser/fan and replacing it with a modern aluminum cross flow condenser and larger pusher fan. This turned my AC from marginal to COLD. I was amazed at the difference this new condenser made.