I just finished Buchanan's new masterpiece Day of Reckoning. He has a lot of differences with Ron Paul, especially in regard to free trade. Both men oppose NAFTA, WTO, etc. but for different reasons (apparently). Buchanan sees us dismantling our manufacturing base, which helped us win WWII; as well as our record trade deficits with China who uses the extra cash to build up her military. Paul opposes (apparently) these trade agreements because they're "managed, and not free enough".
Buchanan talks about the ethnic makeup of the country, and how the succesful melting pot is "rejected as a tool of cultural genocide." He does not mince words, and comes out and says that not just anyone can assimilate and it is PC foolishness to assume that you can invite the whole world and not balkanize the nation.
Buchanan wonders why libertarians (many of them) support importing cheap labor when those workers and their family members will require social services which further strains taxpayers. Buchanan calls free trade a "cult" and "faith based" and completely dismantles Milton Friedman's arguments for it, while calling adherents of so-called free trade ideologues.
Buchanan wants to bring the troops home from bases across the globe, and did oppose entering Iraq. But he does not call for a swift retreat, arguing that the ensuing chaos would be worse than the status quo.
Buchanan also says what is happening on our southern border is more important than anything that happens in Iraq or Afghanistan. We'll eventually disengage from those conflicts, but if amnesty is granted to 20 million illegals and our borders remain open, this the end of the nation.
They're close in some areas, but not so close in others. Even if he were in a position to do so (i.e. not a regular on MSNBC) then I don't know if Pat would endorse Ron Paul, even though he certainly admires the guy.