[kh99]

I think what you can do is to find the css for the forum blocks and change it. I know at least some of it is in the sidebar.css template, which is under the CSS Templates group. For example, there's this:

#sidebar_container .block {
	margin-bottom:4px;
	padding:6px;
	border-top-{vb:stylevar right}: {vb:stylevar border_radius};
	border-top-{vb:stylevar left}: {vb:stylevar border_radius};
	border-top-{vb:stylevar right}: {vb:stylevar border_radius};
	border-top-{vb:stylevar left}: {vb:stylevar border_radius};
}

which sets 6px padding for the blocks. I think if you reduce that it will get it closer to the vBa block look. You can see that the padding and margin have values there, but other values use {vb:stylevar ..., in which case you'd probably want to change the stylevar instead of the editing the template.

I don't know how much CSS/HTML you know, but you can right click on the forum block and "inspect element" (at least you can in Chrome, and I think Firefox has something similar), and
it will open a window at the bottom that will tell you what CSS is affecting that area, then from there you should be able to find the CSS in the vbulletin template that needs to be changed.