Simple source transformation question

[renzoms]

I know I can compute source transformations using the method shown here in the blue index card here https://imgur.com/a/RXwJT3r.

I used both of these methods, in an exercise here https://imgur.com/a/LHiRIjL

My solution is here https://imgur.com/a/0AuJNJ3

Now, I have some questions about this sample circuit here https://imgur.com/a/rO5HozN

I know if I remove Va, R1, and R3 from the circuit, I can source transform Is and R4.

If I remove R3 from the circuit, can I source transform Is and R4? I understand that the possible answers are "No, Va and R1 affect the circuit... don't allow this...", and "Yes, Va and R1 are both strictly parallel to Is and R4 so you can source transform."