I have an original Piper Twin Comanche Owner's Handbook.
I scanned the following from the performance section, the numbers are page numbers:-
SECTION IV
PERFORMANCE CHARTS
Take-off Distance Over 50 Foot Obstacle.....................37
Take-off Ground Run................................................38
Take-off Distance Over 50 Foot Obstacle (Short Field)..39
Take-off Ground Run (Short Field) ............................40
Best Rate of Climb Speed ........................................41
Single Engine Rate of Climb......................................42
True Airspeed vs Standard Altitude............................43
Range vs Standard Altitude......................................44
Enroute Single Engine Service Ceiling........................45
Landing Distance Over 50 Foot Obstacle....................46
Landing Ground Roll...............................................47
Landing Distance Over 50 Foot Obstacle (Short Field) 48
Accelerate - Stop Distance .....................................49
Altitude Conversion Chart ......................................50
Power Setting Table ..............................................51
If you pm me a private email address, I can send you any of the above in PDF format. There is no climb fuel graph.
Quoted consumption - 84 USG useable leaned to best economy
17.2 gph @ 75% 800 sm @ 8000'(std Alt) inc 45 min reserve
15.2 gph @ 65% 860 sm ditto
13.4 gph @ 55% 910 sm ditto
11.2 gph @ 45% 975 sm ditto
I presume the above would include the climb, but it doesn't say so.
You then have to do all the conversions - ANM to GNM, USG to Ltr, Std Alt to Press Alt etc.
Practically we used to use rule of thumb with a fudge factor which was acceptable to reasonable people once upon a time, but I doubt if NASA could satisfy the CASA bureaucrats these days.