Mark;
Is the current converter a GER, or the 3500 you plan on purchasing? If you're planning on purchasing a GER, please PM me first!
Do you know what the "list" number is on your 1050? There are several different 1050's available, some can be made to work well on the street while others can't.
As Rob stated above, those 990 heads have pretty big chambers to begin with. Unless they've been whittled down, they should have around 119-121 c.c chambers. Any chance you have the spec/build sheet from the engine builder?
The reason I ask is, the last 461 BBC I built for a customer had SRP pistons in it that were rated at something like 12.4 with a 119 c.c. head (been a while since I built that, but those #'s should be pretty close). I didn't have to flycut the pistons to clear the cam. With the pistons roughly .010 down in the hole, a .041 gasket and 121 c.c. chambers in the heads, the actual
measured compression ratio came out to roughly 11.8. You can't always go by what the catalog says. Just a few c.c's either way can make a notable difference in actual compression ratio.
As far as the cam/compression deal, running too much static compression with a cam that's too small will build too much cylinder pressure and can lead to detonation problems. That's why it's really important to know the actual compression ratio when choosing a cam. At roughly 12-1, you still have room to step the cam down w/o running into this problem.
If your compression actually is 12-1 or slightly above, I'd look into something like the Crane roller p.n. 138121, which is .663-.638 lift (gross), 260-270 at .050 and has a 110 LSA. The duration is 14* smaller at .050 and you're losing roughly .074" lift on the intake and .088" on the exhaust. This will still have enough duration to work with your compression, but the reduced lift will dramatically improve valvetrain life. Power loss would be mild.
If you'd rather go with a solid flat tappet cam, look at something like the Crane 134691 or 131311 (256*-266* @ .050, .580-.600 and 256*-264* @ .050 and .618-.638 respectively) The 691 cam makes great power from about 4000 up and has a nice thumpy idle. The 311 cam makes great power from about 3600 up and has an absolutely wicked idle. Both are "streetable" cams, but they can be pretty choppy unless you've got the carb dialed in for part throttle cruising.
Sorry for being so long-winded, just trying to cover as many bases as I can.
Eric
