On the last circuit I posted, if you want to use TL072 at vcc=14V, change R3 to 220kΩ. This will give you about 9.63V at the junction of R3 and R4. This is about optimum for 100% modulation at max amplitude without audio distortion. If you want more audio gain, change R11 to a 500kΩ pot, R10 to 3.3kΩ, and C2 to 10uF. This will give you a maximum audio gain of about 150. This is the highest audio gain you can get and still maintain at least 20kHz audio bandwidth. If you can tolerate less bandwidth, you can make R10 smaller, but be aware that you will have to make c2 larger to maintain your low end rolloff frequency.
If you want more gain at full audio bandwidth, you will need a preamp.