Outer Limits 4x4 Board

I'm changing my clutch in my 88 sierra I have a mk 1 GTI motor in it with the std GTI flywheel and I have a std flywheel out of a sierra it came of a G13A the sierra flywheel is bigger than the gti one and starter wont fit I want to use the sierra flywheel as it should give me more toque down low due to being heavier.

the questions I have is :

1 do I just need a starter out of a G13A to to make this work

2 do I need the backing plate of the G13a As well the one that locates the starter motor

3 I there anything eles I need to know?

thanks for any help

heres some pics of the 2 flywheels

mate are you sure you have the right flywheels there? im not sure about the mk 1's but i have the mk 3 motor in my bus and use the sierra flywheel. they were the same diameter, just the gti 1 was thinner.

i use a sierra starter.

That's a 1600 flywheel that's why it's bigger

X2 FOR 1600.