Write new code to live at $1577 and write it over disk block $049D at byte $177:
; $F8 = dest address lo
; $FA = dest address hi
; $162F = block number
1577: 18 - CLC
1578: FB - XCE
1579: C2 30 - REP $30
157B: AD 2F 16 - LDA $162F
157E: 8D AA 15 - STA $15AA
1581: A5 F8 - LDA $F8
1583: 8D A6 15 - STA $15A6
1586: A5 FA - LDA $FA
1588: 8D A8 15 - STA $15A8
158B: 38 - SEC
158C: FB - XCE
158D: 20 8A 98 - JSR $098A
1590: 41 - DB $41
1591: A4 15 00 00 - ADRL $0015A4
1595: B0 03 - BCS $159A
1597: FB - XCE
1598: 18 - CLC
1599: 60 - RTS
159A: C9 2E - CMP #$2E
159C: F0 EF - BEQ $158D
159E: 18 - CLC
159F: FB - XCE
15A0: C2 30 - REP #$30
15A2: 38 - SEC
15A3: 60 - RTS
15A4: 03 01 - DB $03,$01
15A6: 00 00 00 00 - ADRL $0000
15AA: 00 00 00 00 - ADRL $0000
Used Block Warden to set these bytes directly on block $049D, starting at $0177, because I hand assembled it, baby. I've been staring at this stuff long enough to do that. The authors were kind enough to create and preserve a slot-independent entry point at $098A as you'll see in the disassembly notes.