It's not quite that easy... 1 inch longer shocks needs about 5/8 farther out shock mounts to sit at the same level (approximately). So if you add an inch of shock length with the same mount, it will increase the preload ride height by 1 1/2" (again approximately).
The problem with that is the shock mount on the lower arm is put where it is to keep the ball joints from binding using a certain shock absorber throughout it's usable motion range. Putting a longer shock on it, limits the usable range between where the ball joint binds at the lowest point and the shock bottoms at the highest. You really want the shock to stop the suspension travel at both ends, never the ball joint.
Is this realy a problem in your situation? Probably not. The only time you're going to be hitting the bind on the ball joint is when you have no load at all on your arms (jumps and wheelies when the front tires are off the ground) which isn't AS detrimental to the ball joints as the other way around.
The real question is, why do you want raptor 350 shocks on your blaster? New shocks for the raptor and hand-me-down the factory shocks to the blaster? Do yourself a favor and try the new a-arms with the factory blaster shocks before you go changing. It ride will surprise you actually. Because the factory blaster shocks are so stiff but the new arms have so much more leverage on the shocks, they match right well. The blaster shocks don't have as much travel as the raptor 350 shocks but you problably won't be using all that travel anyway and the factory shocks will keep the ball joints happy.