Concerning your current intake manifold, there is a two piece die cast aluminum intake in two bbl and one bbl versions that have leak issues at the seams. But they can be successfully repaired be either welding the seams or sealing the seams with epoxy.
So unless you want to go with a different intake manifold, you do not need to.
It would be helpful if you could post a photo of your current intake manifold. So we can better understand the issue.
If you do change the intake manifold, that change should be made in conjunction with other engine component upgrades. With a 4 bbl you should also consider raising the compression, maybe a better cam and improved exhaust to get your money’s worth out of the larger carb.
