The block casting numbers are meaningless. C6ME blocks can be 352, 390, 410 or 428 cubic inches. All the 428's (including police 428s) in 1967 had non adjustable hydraulic lifters. There is not one thing in the valve cover area that is different on a 428 compared to a 352 or a 390.
Pull a spark plug and measure the stroke. If it is 3.98 you have a 410 or a 428. All the head castings and intake castings and block castings are the same for 410 / 428 / 390. No way to tell without pulling a head and measuring the bore to see if it is a 428.
You didn't mention what the engine code was in the VIN - that might tell you something.
I agree with the forum, what little literature I have does not support a P.I. in a 67 TBird. Took a better look at it today. The header flange kept me from seeing weather the exhaust bosses were drilled or not. The valve covers are plain height for hydrolic rockers and the date on the block looked like May 1st 1967. That date on a C6ME block would be correct for a 428. The two 67 390's I had were C7AE casting: www.mustangtek.com/block/Block.html supports what I have learned over the years. The pulley might be the C5AE-D over a C4 ballancer. It has the large port oil filter adapter. If we buy this truck I'll post what I find.