I think what you're asking is if the parts that you might buy for the 305 that's in it today can be used on a 350 that you'll spring for later? Say you're wanting to change out the intake you can spring for the one you'll eventually want for the 350 knowing that it might not be the absolute best choice for a 305, but it'll fit and will offer some level of improved flow, efficiency and performance for your 305. Specific to your question on the distributor, like Ken & Glenn said you can feel secure buying a top quality electronic distributor for the 305, knowing that you'll be able to drop it into the Gen I 350 that you get later. Watch out for counterfeit junk out there in the electronics arena. Buy from a reputable vendor and don't be tempted by the evilBay bargain basement prices on what looks like the real thing.