[align=left]Man... I thought this post was buried in the back 40 with all my ex's. Thanks for finding it!
I wish my tank sticker looked that good. Thats a freakin novel compared to mine. You can identify a 4 bolt 3999289 block from the outside without removing the oil pan. On the oil filter boss there are 3 plugs that cap of passages for external oil coolers. A 2 bolt has a 5/16, 3/8 and 1/2 front to back in that order. A 4 bolt has 1/2 and 1/2 and 3/8. There was a good picture of the 2 bolt pattern in Glens reply to my original post titled 73 LS4 from 2005 in C3 forum. If you can't find it let me know, I'll copy some pictures and post them. Let me know what you find out.
Wedge

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Thanks for the info on the oil passage bolts,
now I shouldn't have to pull my pan.