I converted a leaf blower into a vac & it works very well, within it's
limitations. It was a 5hp blower & I wouldn't recommend anything
smaller. It has a 6" intake hose, 6' long. A smaller diameter will
clog too easily (there are ALWAYS some twigs in the leaves) and longer
restricts the flow too much. The hose is honest-to-god vacuum hose &
well worth it ($9/foot, IIRC). The fan discharges directly into the box
of my leaf wagon. I've not tried discharging through a hose & wouldn't
even try - it would add too much restriction.

This is a case where bigger is not only better, it is essential. Trying
to get by with shop-vac sizing will be excruciatingly slow. I have a
hand-held blower that came with a conversion to use as a vac, with it's
own bag. I used it for about 10 minutes before trashing that part.

HTH, YMMV, etc,
Bob