Reg Cab VS Ext/Dbl Cab leafs, OME VS Bilstein struts/coils

Hey guys, Im new to the site, But have spent quite a bit of time searching around.
Honestly have become a little confused by a few different scenarios..
So let me run this by you guys..Sorry if this has been talked about and cleared up elsewhere, like I said Im new..
01 2.7 4x4 Reg Cab w coil spacers front. Stock Struts, blocks and extended shocks rear.
Seems as though the leafs in a Reg Cab are shorter in height (not length from shackle to front Bolt) than the leafs in an ext or double cab..so would it be possible to remove my stock leafs and simply swap them with a set from an Ext Cab or Dbl ? If true, ordering aftermarket leafs for a diff wheelbase "should" work also?..
sick of the blocks in the rear, either going to AAL or buy an entire new pack..either aftermarket OME or just pick up a set of stockers for diff wb
Also theres so many companies that offer UCAs for my truck...is it really worth it?
OME struts and coils in front? or Bilstein ? And what combination strut/coil would be best with the new leafs/AAL in the rear?
took calling around about 9 diff shops in the upper valley where I live just to get a set of 2.5 x .5 x 10 U bolts.
I know this isnt the most organized post, but I NEED HELP
THANKS in advance!!!!

 

and while im at it..
Anyone know where to get a Plastic Fuel Tank for the same truck? 01 4x4 2.7