Yes, both the SR3500 and SR3001 will work with the original (gray case) Spektrum SM1000 modules. On the Specs page for the SR3001:

• Will work with any of Spektrum’s other transmitters or module systems
• When matched with a standard DSM surface module system, DX2.0 or DX3.0 transmitter, it will decrease latency by 1.3ms

So you don't get the full Pro Series latency benefits, but both RX's will operate with the SM1000 modules just fine.