If you are going to go "all the way" or even "most of the way" with your modified Lenco, then it will merit the best tonearm you can afford and fit to your plinth. Beyond that, I don't believe there are any limitations to be based solely on the fact that you have a Lenco vs some other brand or type of turntable. It's more important to match your tonearm with your choice of cartridge.
I have a highly modified Lenco in a slate plinth. I chose a Dynavector DV505 tonearm for that turntable, mostly because it is one of only a limited number of tonearms that can be surface mounted. (Others include the Triplanar and the Reed tonearms.) Surface mounting makes it unnecessary to create a removable tonearm mount that would need to be drilled out. So my choice was largely pragmatic: the DV505 is excellent, is less expensive than those other options I named (though I do own one of each), and was convenient to mount.
