Front end pieces 75 to 69 what will work..

You're in luck.
If you transfer ALL of the parts from your '75 to the '69, it will all bolt up and work properly. Using the '69 slant 6 k member will be fine. The only real difference between the two is the way the engine mounts are configured, '73 and up are spool mounts and '72 and older are biscuit type.
Do not mix and match the suspension parts between the years or you will be sorry unless you know exactly what you are doing. Torsion bars will interchange between the years too.
Great time to do a V8 swap......
Just kidding!