Just a couple of easy questions... If you please

[ChuckW]

So... In the stages of engine swap in my 1966 C10 fleetside. 283 out and early model 350 in. Stock tranny is an old granny 4 sp. I'm keeping this box.. My DUMB question is how is the shifter removed from the top of the box? Is it actually a quarter turn lock type retainer?
Ques. #2. anyone know a header P/N model that I can use with no clutch linkage mod?? Seems most I can find come with a disclaimer of some sort "maybe requiring clutch linkage mod"??
#3. It appears (from what I can gather) that the 283 flywheel will work just fine with the 350..... Is this true?
I'm so looking forward to getting her back on the road! Has been a couple of years and the light at tunnels end is getting bigger!
Thank you for any help and or advice!!!
PS
LPG conversion soon.... Anyone know of a good installation... Needs to be able to run both Gas and LPG....
Thanks!!
Cww