i heard you have to modify these to fit. what needs to be done? also whats the diffrence between 65385 and 65387 thanks in advance

 

Don't know the difference in the two.
On the shop car we had to mod the #1 cyl to clear the LS1 steering shaft and #8 to clear the air cond box. If ya don't have air then #8 will fit.The top half of the tube had to be remade on #1 and the tube cut in the bend and brought closer to the flange on #8. The air conditioning compressor has to have most of the hump taken out of the metal line.
Don't know of anything else,havent gotten that far.
I do know one thing,the plugs on 6/8 are going to have to be changed from the bottom.