Need your love so bad

I don't know that the guitar is important. That song is a Strat with little sustain. He keeps the notes going with finger vibrato.

Sounds to me like the amp is running fairly hard and is breaking up a bit when he attacks the notes so there will be a bit of natural power amp compression happening. The main thing that Peter Green is using though is probably volume. Standing pretty close to a moderately loud amp will make the guitar vibrate a bit and contribute to the sustain.

To get it with the Kemper I would try using the amp compression for starters. If that doesn’t work then try the compressor effect with a healthy amount of compression but a slow attack and maybe a mid to lower level of mix. That way the attack of the notes should come through without compression to keep the bite and dynamics but the tail of the note will be boosted by the compression. Another option would be to use a slightly more distorted sound with the guitar volume rolled back about half way. As the note dies away increase the guitar volume to add sustain.

Try a compressor for sustain. It's what I use my Keeley Comp for.

Quote from theplayer

Yes, I now. I do that allready but it's hard to find that sustain without distortion.

It's hard, but to my ears it's a tone without sustain, but he's keeping the notes going with great finger vibrato. It's hard, but there's no compressor that will give that.

I agree that a loud amp in the room is probably helping to keep the notes energy.

Compression parameter in the amp section.

A Strat also has more string tension than a LP, so that's also a factor with low gain.

He played that sound loud. If you do that, you will get that guitar to speaker interaction.

....and reduce/switch off the noise gate.