The 3/8" spacer does fit with the Cobra upper under the stock hood, my dad runs one on his 93.
I run the 1" on mine and it keeps the upper 75-100 degrees cooler I have tested it to see how much difference it makes. The longer runner do take a way you top end a little it may make you peak at 200 rpms earlier then normal, no big deal when your turning 6300 anyway.
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