I`ve never played with blowers or turbos, although I have run plenty of nitrous oxide thru FE`s years ago. My nearly bone stock R code 69 Mach 1 improved from mid 13`s in the 1/4 mile, to high 11`s at 115mph with a 125HP NOS kit. Stock exhaust manifolds with crappy crimped 2 1/4" $100 dual exhaust system, stock torque convertor, 3.50 gears, cast pistons, stock fuel pump, the only problem I ever experianced was bending several stock pushrods when the engine overrevved due to wheelspin on the street "on the bottle" in low gear. Shifting at 5600 RPM, this combination was virtually bulletproof for the 2 years I ran it like that. However, the first 390 I had in my Fairmont suffered major destruction "on the bottle". It used a "105" D4TE block, main studs, new Lemans rods with forged pistons, and ran mid 11`s @ 114 MPH with a foot braked C6. A 175HP NOS kit pushed the car to 10.2-3ETs at over 130 MPH, but after about a season of such useage, ALL the main webbing between the cam & the crankshaft tore out of the block, the crank was in 5 pieces. The right side of the oil pan rail area was bulged out noticably, the starter nose snapped off, and the flexplates starter teeth had carved a large groove in the bellhousing area, as well as splitting the entire bellhousing area from pan rail to pan rail. The front pumps stator support was also snapped off. The photos were posted on the FE forum about 10 years ago by Dave Shoe. This carnage happened in 1989 or 1990, and I`ve been naturally aspirated ever since. I think Jays analogy of the big tired, 6000 RPM clutch dumps being hard on the non crossbolted FE have much merit: after the 390s demise, I have ran 4 or 5 different 428`s thru the Fairmont. 2 died from broken connecting rods after years of racing, when used with the C6, but the several split cylinder walls,& cracked main webbing has all occurred in the last 12 years since I replaced the C6 with a 4 speed Jerico & clutch. The performance improvement with the 4 speed is considerable, but it sure appears the added stress to the block is as well. Although a crossbolted block would certainly help, its no garantee that split main webs will never happpen. The 427 block in DaleP`s 67 Mustang suffered a split main web, right thru the main bearing oil hole, just like my 428 did.