Chainsaw Repair

I've been looking for one for several years with no luck.  But if I do you will be first in line.   I've thought about a HDA 137 or 164 16.66 venturi from Poulan 330-3750 change shafts if needed but these carbs use a impulse line from top of carb to impulse barb in the crankcase.  You could drill crankcase and install impulse port.  If I can get caught up I may try it on the last 261 I picked up.  I'll have it apart anyway. 

IIRC the HDA 87 was replaced by the HDA 120/120-1. Does anyone know what the specs changes were  between the 87 and 120?

120 is 15.08 same as 144 IIRC.
Shep