My Spring Project

I would like to start off saying: Like many of you I have a passion for the fox mustang and love Stangnet.com and everything they've done for us. However, unlike many of you I am not a mechanic guru, and do not have alot of knowledge about the fox and its parts. Thus, I come for support and second opinions.

I've searched 50tech and 50talk for plenty on the 4 to 5 lug conversion so I'm not trying to waste anyone's time with this post.

Currently, I sit on Chrome Ponys, 4 lug. Car is not lowered, however I would like to drop 1.5 inches in the future.

I would like to know if this set up would work,

Conversion kit provided by 50resto.com 87-93 CONVERSION KIT, 5 LUG, WITH 31 SPLINE AXLES MUSTANG. They offer this conversion with 31 Spline axle, and 28 spline axle. Which would I need, and whats the difference?

Here are the Wheels: http://cgi.ebay.com/ebaymotors/18-x-9-Chrome-Mustang-wheels-rims-tires_W0QQcmdZViewItemQQ_trkparmsZQ7c301Q3a1Q7c293Q3a3Q7c294Q3a30QQ_trksidZp4634Q2ec0Q2em14Q2el1262QQhashZitem58813e3736QQitemZ380125460278QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
In case the link dies, Here are the specs.
Wheel: 18 x 9" - 24mm - 5 on 4.5
Tires: 245 40 18ZR

I'm really kind of in the dark here guys, so any light you could shed on this set up would be great!

I read about flattening the dust caps. Just practically taking a mallet to them- Do you think this will be enough to clear the center caps in the 5 lug swap kit?