You have trouble building a 305 because its a piece of ****, not because of the bore and stroke.
There is a trade off between the 4.6 and the 5.0 and I have certain issues with both. The 5.0 benifits from its simplicity and that its been around since the 50s so its been fiddled with and its exploited exploited since then. The 4.6 is newfangled. Parts are more expensive. The timing chain arrangment could be better. The oil return from the heads could be better.
Anyway, a fast 4.6 is deffently more friendly then a 5.0, especially when made fast, and that's probably why they are more popular with the general non-racecar building public. That and a American V8 turning 7000 RPMs just sounds wonderful.
