Video of rudeez's build:
Here is the version with transistor input and output buffers:
Both should fit comfortably in a 1590B.
Many people have reported good results without the output buffer, and so it may be worth trying the most simple option first to see if you're happy with it.
There are so many ways you could do this. Omit both transistors and use one half of the opamp as the input buffer with no output buffer. Have a transistor input buffer and the unused side of the opamp being used as an output buffer etc etc. The possibilities are endless.
Possible mods that have been suggested, if you find the effect muddy then consider swapping the 22u and 47u caps for 220n and 470n respectively (some people believe the 47u is definitely wrong and was actually .47u and just misread). It may be worth socketing those caps so you can experiment. Some people have reported that the 220p cap should in fact be 1n, but others have said it sounds better with that cap omitted entirely, so again it may be worth socketing so you can swap and remove to test. Suggested improvements to the tone control is to swap the 27n cap for 33n, and swap the 100n cap connected to Tone 1 to 47n. Socket and see.