The MC1350 (and cousin) is a difamp input and depnding on frequency is about 3.5K.
Its easily loaded down to lower impedances with a resistor or equivilent lumped circuit.
The output impedance is around 4K collector to collector for best signal handling.
Typically its a resistive load that determines it for a transformer its often loaded
with a resistor.
NOTE the MC1550 is NOT the same as MC1350 it is a lower gain committed dif pair
very similar to the CA3028 though less versatile. I have a few of them and they made
fair IF amps with AGC... Same noise issue as 1350. Had to dig out the Motorola
1971 Linear products databook for that one. Input impedance single ended was
about 1.5K and output impedance was fairly high. The gain overall was lower
than the 1350 and you would need two for the same result. I used three in a
SSB transceiver back in '72 two for the IF and one for the product detector.
I used them as at that time and place I could get them. CA3028 would have
been the part I wanted but they were scarce then and a tiny bit more costly.
The suffix on the part was often a partial indicator of can or plastic. The MC1350P
was plastic 8pin only (for TV circuits and uses). The MC1550 was available in
'71 in TO8 can. So all the 1350s I have are plastic and all of the 1550s in the bin
The MC1496 made a fair attenuator as well as being a mixer and multiplier.