The 1 5/8ths journal ARP rod bolt set is a slightly different format part number: BE6001

//www.minimania.com/part/BE6001/Arp-Connecting-Rod-Bolt-Kit-1275-1625-Rod-Cooper-S

....of course also for the inline 1275...

The 3/8ths bolts (small-block Chevy size) won't let the rod fit down the bore with the 1 3/4 rod-journal cranks, so the 1275 A & A+ (all but the original 1275 S) got 11/32nds rod bolts (small-block Ford size.... still plenty stout but a good upgrade to go ARP).

You can use ARP 155-6002 bolts (Ford FE bigblock) instead of the 206-6001 (Cooper S) bolts. You get 2x the bolts for less $$, and material specs and bolt length is the same. Head is different shape, but they fit.

[edit] was a typo in p/no.

Thanks for clearing that up....I'll let him know.

There was a big journal rod used before the A+ rod, in the 70s. These rods had big lumps on the caps, and used 11/32" bolts.

@Steve CooperTune, I believe they went to these smaller bolts as there is not room to swing a big journal rod with 3/8 bolts in.

All in line 1275s as supplied in Sprite / Midget were 1 .625 rod journal. Just the Austin America 1275 transverse and A+ 1275s carry the 1 .750. Oddly small journal rods carry 3/8 bolts and large journal rods 11/32 bolts. Steve (CTR)

Interesting, thanks for the response.  

The engine builder I spoke to back east seemed to believe that "early" 1275's had the small journal cranks, and that the change point was the A+.   Now, having said that, his bread and butter is in-line 1275's for Spridgets...were they different in this respect?   Were so e of them small journal cranks?

Noted in the ARP listing the 206-6002 is 11/32" size for A & B series engines, this would include pre A+ and A+ applications for rods using 1.75" journal size.

206-6001 is 3/8" diameter as used in the Cooper S rods, 1.625" journal size.

As the bolts are different sizes for different applications they are not interchangeable, and the larger diameter of the 6001 bolt would account for it's increased torque value.
( I prefer to stretch the bolts to the specified value rather than torque.)

I just had my pre-A+, 1275 rods shot-peened, resized, and balanced at a well-known shop in SoCal.  The shop supplied the ARP rod bolt set, and it appears they used the 206-6002 bolt kit.  

According to the ARP website, it appears the 206-6001 kit may be the "correct" kit for the early 1275 rods, and the 206-6002 kit is for the A+ rods.  I spoke to a race engine builder back east who specializes in A-series and B-series engines, and he was pretty adamant that the 6001 kit is for pre-A+ 1275's, and the 6002 are for A+.....so he agrees with what ARP seem to indicate.  

Interestingly, our host lists the 6002 as being for all 1275 rods, and doesn't appear to carry the 6001 kit.  Does anyone know what's going on here?  Has the 6001 kit been superceded by the 6002 for all 1275 rods?  

The thing that is most concerning to me is that the 6001 torque spec is 55 ft/lbs, and the spec on the 6002 is 35 ft/lbs.....that is HUGE.