Just as a follow up to this, beatcracker suggested this to me in PM: "Hi, I had a quick glance at your race.bin and it's the same bug (add 0x96000h to the videomem size), but hex-string to search is a little different: 8144240400600900. Replace it all wi 90 and it should work. If not - I'll look at it more closer."
I can confirm this WORKED for me, the game now runs. However it falls into 2 other problems: firstly there are many textures (black parts of dashboard/in-car model) that are now transparent. This can be cured by using dgVoodoo's Direct3D fixes (and probably by other solutions like DXGL or WineD3D). The replacement DDRAW.dll method (or ACT fix) from http://www.blitzbasic.com/Community/post.php? … 77&post=1202630 when applied to race.bin in the Data folder improves framerate also (although using dgVoodoo etc will probably do the same).
The second problem though is sound. It's all crackly and makes the gameplay slow down. If I apply ALchemy to the race.bin file then the sound won't play at all, but the gameplay will be much smoother (unlike if you simply disable sound in the game), so it's something to do with audio playback. I had a fiddle with options.cfg in the Config folder, but that didn't help at all.
So, really, it's 90% there. Does everyone need a separate fix though, depending on how much memory their graphics card has? I'm wary/worried that many other failing games might also have problems with the amount of graphics memory available... currently I have 55 games broken (not just for this issue!) and 423 working (tho many of those are DOSbox so that's not really the same thing!).
My PC spec: Win10 64bit, i7-4970K (not overclocked), KFA2 GeForce RTX 2070 SUPER, Creative Soundblaster ZXr, 16GB RAM, Asus Z97-A motherboard, NZXT 410 case, ROG Swift GSYNC monitor