You can also try adjusting the audio detector coil A.K.A. quad coil.
Flag your diddle stick to be SURE you can go back !
Adjust for less buzz. Center at the least buzz point. If it takes
more than a turn I would go through the audio with new det tube & a fine toothed comb.
The SIF transformer will only effect hiss.
BTW Motos often had an "optimizer" adjustment, try that first.
SAW filter is over the top IMHO. A fun project if you are into
such things would be trying an IF strip. Get a Zenith 150-190-01
IF module & adapt it ( must be the -01 version ! ). You will need 24 V
to run it & AGC voltage. Output will be composite video & SIF. A
crazy project but who knows ?
73 Zeno
LFOD !
BTW BUZZ SUCKS