6502.org

It's never too late and thanks so much for sharing your thoughts, Gilhad I've made some final adjustments after all the comments (including yours) and ordered a PCB for the entire $25(from JLPCB) including taxes and postage. Will let you know how (or if) my board works once I have it.

I have finally decied to stay with my line drivers. '245 looks like elegant alternative, but as I have 11 LEDs to control.... 2x6 outputs seems more reasonable. As adviced, I use OE/ signals to control leds drivers. Regarding the via in a surface mount pads - I've decided to leave one like that for testing purposes and see how it will go. JLPCB describes specific parameters of such vias, so it feels like common practice.
Good idea about the jumper, but I have no single pin left on my Teensy to read the configuration, so I'm going to leave it to the software - one would need to enable either '816 or '02 version on that level. Perhaps for futer iteration of the project I should move from parallel access of address/data lines to some fast serial shift registers. That feels like an out-of-topic question for this post, but curious whether you have some experience with it.
Thanks for the advice. For this project I've been using EasyCad and its configuration options are limitred comparing to KiCad (that includes color settings). I quite like EasyCad due to its great library of components and footprints, but it annoys me massively due to the lack of support for active-on-low names (with overline).

My project http://8bit.gilhad.cz/6809/Expanduino/Expanduino_I.html is based on them Basically it is Status Register and 3 Read registers (74HC595) plus 4 Write registers (74HC165) presented to HD6309 (but it would work as well for 6502 or anything similar) as 4 R/W addresses, while for Arduino it is presented as 8 SPI devices (1+4 read, 3 write)

The project worked, but I am now onto something bigger. The pages are in Czech language and with KiCad schemes in default yellow/green (but with sources) so it may be problematic to read. I may convert it to BW sometime later.

Here are schemes http://8bit.gilhad.cz/6809/Expanduino/E ... tml#schema and sources http://8bit.gilhad.cz/6809/Expanduino/E ... l#zdrojaky and errata http://8bit.gilhad.cz/6809/Expanduino/E ... tml#errata anyway. (Clear on '595 is active in zero, so should be conneted to +5V, not to ground. SD_Enable signal should be negated.)

Ok, so it arrived. Will let you know after weekend whether it actually works
I know it does very little and is a small project, but as it;s my first PCB, the satisfaction is great. Or... well - there will be when I see it actually working.