On the tranny gear ratio you can put the trans in first gear and mark the input and output shafts and tranny case so you can turn the input shaft and count the amount of turns it takes it to rotate the output shaft one complete revolution, if it takes a little over 2.5 turns it has the 2.66 low gear, if it rotates a little less than 2.5 full turns it has the 2.42 low gear
As far as all the original AAR and T/A heads and blocks the heads have the intake pushrod holes move over away from the stock location and all of them have to use offset adjustable rocker arms, they came with them stock with ductile iron adjustable rocker arms and matching pushrods, same cam and lifters as the stock 1970 340 motors had but different rockers and pushrods None of them came with the small valve heads, they should be either O or U castings, maybe even some J castings but maybe not on that last one
IHTHs