4.8 vs. 5.3, same truck and gearing...?

[mopower440]

All years will work, iron head models are weakest. If its a year with the longer crank run the flat flexplate and adjust the 3 converter holes. If its the short crank either run the spacer with a flat flexplate or no spacer with dished flexplate

ok, what years would have the longer crank and what years have the short one? also, what do you mean by adjust the 3 convertor holes, and, what is my stock flexplate in my 1999? Im sure i will get wichever one is most available so im assuming that would be the LQ4? what years would they be found in and what would i need to make that one bolt to my stock tranny, the spacer or the altering of the bolts? Or better yet, i dont care wether its an LQ4 or LQ9, just using it to replace the 4.8 when it dies, so a better question would be, what years would be the easiest to drop in and bolt to my stock 4l60e trans with the least modifications or rigging?
thanks again, awesome info here!