UPDATE ON GEAR:

i had to cut the side plastic of speedo head(be EXTREMELY cautious when doing this as the plastic may crack to other parts of the head you dont want cracked-i used a cut off wheel) popped the board out(be careful of OD stepper motor it can and will pop off requiring a new motor or disassembly of motor and resoldering pins to windings) i fortunately had a spare board so popped the "new" tape deck gear in soldered the board in(blue and black wires were soldered and heat shrinked) and reassembled everything.

drove the car for .8 miles around the block and mileage registered PERFECTLY so im good to go for another 20 years. this gear is a bit tougher also so it may outlast the speedo.

BTW the speedo boards from the 240s are exactly the same boards as the 740s but only like 1 part(the YELLOW rectangle box i think its a crystal) is diffrent just use a 740 spec. crystal and youll be a-ok all other parts including the board itself is completely interchangable.