An obstruction at the blower input is a possibility, but I'd also check your vacuum operated air doors and ensure they are working correctly, otherwise the air might be blowing great but no idea where it is coming out. On my 89 Suburban the vacuum line from the intake thru the firewall to the HVAC controls was broken - could hear the blower spinning like mad but didn't feel much.
I also have an AMC era Jeep that the air never blew worth anything (heat or AC) - turned out there was a peice of paper stuck over the inlet for the blower...wasn't much readable after 30+ years but what was still slightly visible looked like the remnants of a factory build sheet probably stuck in there since it was new.
