I suppose you're looking for a kit for this - I must admit I'd build it on tagboard, enabling you to modify things later.
Are you intending to have one input which can take either microphone or instrument? Or be able to use the two simultaneously? (mixing preamp)
There are some differences between a mic and an instrument input stage; the guitar input wants as high an input impedance as practical (easy with tubes while, for me the mic input wants an input transformer with a low impedance balanced input (with a break jack for a high impedance mic in case it's required) and variable gain. Equalisers (tone controls) tend to be different, to; the instrument input tends to be flat with the pots "flat out", with massive attenuation at chosen bands, the mic input flat with the pots in centre position with a fixed gain/ attenuation (typically plus or minus fifteen or eighteen dBs)
What was the output of the preamp intended to drive? Tube outputs are typically high impedance (or at least low current drive), although this is easy enough to compensate for.
Any of these details is easy enough to allow for if you are working from scratch; a nice little power supply (stabilised 12 volts, or six if you're intending to experiment with different tubes in the future, and +120 - 160 volts plate voltage), a chassis with a few more b9a socket holes punched than you expect to use, a face plate with the input sockets and controls, tagboard neatly mounted (if possible not blocking access to the sockets), and you can experiment with a minimum of risk; it's almost impossible to make it sound really bad (lots of munufacturers tried, back in the sixties) if the tube's within published conditions, though it may get a little noisy.