Inline 250 power brake upgrade help

[Scottcoda]

I have been slowly collecting the parts I need to complete my front disc conversion and I have found that performanceonline.com is having a 10% off this weekend (code 0515) so I thought it would be a good chance to pull the trigger on my master cylinder but I have been recently considering doing a power brake upgrade.
My concern is with a possible clearance issue with the 11 inch booster being brought forward due to the bracket that goes to the firewall.
I was also considering doing a dual 8' diaphragm which is not as wide but looks much longer.
To throw more into the pot I found this 8' dual set up with the proportion valve under the MC which I have never seen before and is a few hundred dollars cheaper but is on ebay. see link http://www.ebay.com/itm/331486111054...%3AMEBIDX%3AIT
Not sure which way to go or to just forget the power brake upgrade..
Anyone who has done a power brake upgrade with my kind of set up, advice would be greatly appreciated.. or any advice from anyone for that matter!!! Thanks in advance.