1-3/4 Headers? ok for appl.?

will going with 1-3/4's longtubes be to much or can you not go too big on headers as far as up to that point.
app. gt-40 U/L intake, gt-40 heads, stock cam,
i can ge ta good deal on a pair, and if it'd be just as good for me to go 1-3/4 while i can get a good price i will, instead of 1-5/8, i heard there were some port opening differences on some of the 1-5/8's also.???

any info would be great. but if the 3/4s are going to drop back pressure ( i don't know if headers do or if its in the H and rest of exhaust that can when you go big) anyways, i don't know alot bout it soo ya. HELP PLZ
 
Basic info .... ANY opening of your exhaust is going to lower back preessure.
The bigger the opening, the more back pressure is lost.
Best you weigh the pros/cons before making a decision
 
too big. if you go that big with those small heads then you'll sacrifice torque and won't gain any top end. maybe a good deal but for your car its not worth it. that size of header is more for 500+ hp cars