Here's the version with those POKEs applied.
There's only one thing left stumping me. I tried to improve the game by adding a high score, displayed on the instructions screen. It only took a few lines of code, seen here (NH is New Hiscore):
We set up BM and BS (best minutes and seconds) straight after the save so that they don't get reset after you beat the high score. Then if you complete the course (lines 440 and 450) we add a line at 460 to go to the little routine at 8800 and check for a new high score.
We can add the routine at 8800 no bother, but as soon as we add the 460 GOTO 8800, the game will no longer run. As soon as the race starts it crashes with a C error at a random line (often a line that doesn't exist in the code, in this case 7196).
The code REALLY doesn't seem to like you changing stuff anywhere between lines 1 and 3100.
And there's another problem. After you have one game, the BM and BS values get wiped, presumably by the CLEAR command in line 1000 that I can see no purpose for, and then the game crashes when it tries to display the high score. If you delete or REM out line 1000, or move it to line 890, or add 999 GOTO 1001, you get a 2/1100 error at the start of the race, which makes no sense. (Line 1100 is just a NEXT X.)
So I tried replicating lines 900-970 at 8700-8770, changing all the RUN 900 lines in the code to GOTO 8700, and adding 8780 GOTO 1005 to skip the CLEAR line, but when you change line 3080 to a GOTO 8700 you get the 2/1100 error at the start of the race. (You can change all the other RUN 900s to GOTO 8700 and it's fine, it's only this one that screws it up.)
I've tried everything I can think of, but I'm defeated now.