Pete, I have a '66 Convertible as well..but a 6 banger- although I have owned quite a few V8 mustangs... Here's what I suggest.. I would search ebay for some clean original exhaust manifolds...They are always up there...but the problem being that they are 40+ years old and made of the same old materials and have already gone through the rigors of being on a V8 for 40+ years so you may find some clean ones, but your chance of cracking/leaking failure rate is high...but if you can score some clean originals at a good price why not... The new repro Exhaust manifolds through NPD or most parts vendors (The good ones should come with a C4, C5, or C6 part# on them already.), If they don't have the part# molded onto them, Then they are the EL CHEAPO ones...Stay away from them.. The new repro ones with the part number on them are excellently made and equal or fare exceed the originals IMHO.. The only physical real difference is that they do not have the "FOMOCO" stamp on them.. That's about it..but they are excellent....so you have to weigh your own options there.
With the radiator...If it IS an original... There are ways to tell... It should have FORD part#'s on it... Then pay to have it recored... Original radiators are hard to find...
You can pick up a repro- Four.seasons/GDI/Proliance/Modine (Did you know that the radiator is the same from all four of these compainies now
All four of these radiator companies have merged into Proliance/Modine .... These radiators are distinguishable, are rounded at the sides and have a white w/blue wavy lines tested sticker at the top.. and are the ones usually seen on most classic mustangs today. Only problem is that if you drive the car regularly, These radiators which go for around $235.00 only seem to last about 5 years...and they all burst/leak in the same place (Where the top tank seams are near the fill hole..definately something this radiator manufacturer has to work on IMHO) I have gone through like 5 of these radiators over the years...and one actually burst and destroyed all the paint on a restored engine compartment... I wouldn't trust these radiators more than 3 years tops...At first sign, swap it out for a newer one. The ultimate is a Griffin aluminum radiator...but it will cost you.. around $600.00.... so there are your options on that..
Finally... With tires...It's pretty much your own choice... I usually buy my tires are Pep Boys. I go with Cornell 1000's White walls...They are a good 50,000 tires...Give the right classic look.. Go with 205/75/R14 or 205/70/R14's .... My favorites size for the convertible is 215/75/R14... This tire size is awesome and gives plenty of Meat on the road...but they are getting hard to find....Pep Boys used to carry them, but not anymore.. Goodyear still carries them in White walls... So those are just a few examples...Have fun...
1966 Sprint 200 Convertible
Melbourne, FL (Formerly from Long Island, NY!)
1965 Mustang Convertible 200cid I6, 3spd Manual
1966 Mustang Sprint 200 Registry Owner/Moderator
1966 Mustang Sprint 200 Convertible 200cid I6, C4 Auto
2007 Mustang V6 Convertible w/ Pony Package