Wheel spacers?

I am planning on leaving my car SBP and want Ralley wheels for it. This limits my choices. Today a friend told me they make SBP to LBP adaptors which add about 3/4" to the outboard offset. Has anyone here used these and if so does one need to buy deeper offset wheels to compensate for the added width. BTW, I am still in the market for a set of ralley wheels as the last deal fell through.
TIA, DM

I have bolt on wheel spacers on the front of my 68 - not conversion spacers but 4.5 x 4.5 because my new cragar rims wont clear the aftermarket larger disc brake set-up I have. They add 1 inch to the track each side and I havent ever seen 3/4 inch spacers (small to large bolt conversion or otherwise), the minimum being 1 inch. That's a big difference over stock front track, but whether you're going to get tire clearance issues depends on the wheel tire combo you're running. To be safe, I'd suggest that you would need to look to compensating with larger backspacing on your rims.

For example, my previous 15 inch rims were 3.5" backspacing and they cleared the brakes. My new 15 inch rims are 4.25" backspacing and so my wheels with the 1 inch spacer now sit out an extra quarter inch from before, which is enough to make me uneasy about tire clearance when I finally get the car on the road.

PS. Stockton Wheel make conversion spacers (I have stockton spacers on mine, made in USA). You can also find them on ebay, made in China most probably.