Doesn't work like that
You are not going to get an opiate high from ANY benzo, plain and simple!
That's like asking what's the best alcohol to drink to feel like I just smoked a bowl. It doesn't work that way.
Because of your question, I assume you want an opiate-like high, but do not want to take narcotics/opiates. Have you ever heard of tramadol (ultram)? I have never had it, but it is a non-narcotic painkiller that apparently has opiate-like effects. I've heard people swear by it on other boards and apparently it will ease symptoms of withdrawal as well. Anyway, check out tramadol. I believe you could get it online rather easily as it's sch. 3 or 4 or something. Check out some pharmie forums and I'm sure you'll find it.
Also, abusing clonidine is pointless and dangerous. Clonidine in small amounts (0.1-0.6 mg) is great for easing some of the symptoms of opiate withdrawal, however, it's pretty worthless as a drug of abuse. I guess maybe a junker with a huge habit could take lots of clonidine and be on some kind of weird, sick nod, but I don't think it would be pleasant. If someone with a little tolerance took clonidine it would just make them sleepy. It REALLY lowers your blood pressure too (as it's primary function is as an antihypertensive), so it could be very dangerous. Since this is a harm reduction site, I must say that I don't think the risk is worth "buzz" someone might get off clonidine. I'd steer clear unless you're in the first week or two of opiate withdrawal.
Peace,
Stoddard