You can still buy all the ICs, the 74HCT are an ideal replacement, the WD-1773 can be found on ebay, ie. https://www.ebay.co.uk/itm/362668881645 ... SwnDRcXYEn - be wary of IC's from China, I've had my share of remanufactured duds (or more to the point, completely different IC's rebranded with the code your expecting!!). The PAL can be found here, https://www.ebay.co.uk/itm/383594580439 ... SwSTFe6lWG. It shouldnt be too difficult to work out the PAL fuse map as the inputs and outputs are known, just need to connect up a parallel port to the inputs and step through noting the outputs to recreate the boolean equations, you could probably even guess them as it is simple decoding.
One thing to note on the design is the missing Schottky drivers. I say this as I have had issues with the SFD800 and a Lotharek HxC Floppy Emulator due to a long (~1m) ribbon cable, a shorter cable gave me no issues. Without the schottky drivers you may find similar issues with signal reflection and degradation (but you may be able to compensate inside the FPGA as it makes it a lot more flexible).
ps) The Chimay is needed, it lubricates the electrons
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