Is there any noticeable difference in reception between the 2 inch and the 4 inch antenna?

I don't see any difference in the city. It does lose stations a few miles earlier when travelling way out of town. But otherwise its the same. Unless you live very far away from the station you want - you won't notice any difference. I love my 2" stubby.

What is the thread size and pitch of the antenna?

There are two threads included for this Stubby Jr., both of which have been verified with factory MINI threads.

Will it fit a Nissan frontier

No, this product is for a MINI Cooper, you need to search for a Frontier Stubby... https://www.amazon.com/CravenSpeed-Antenna-Replacement-Frontier-1998-2018/dp/B00757GT1U/ref=sr_1_2?keywords=nissan+frontier+stubby+antenna&qid=1549645951&sr=8-2

ASIN	B0073XMXMK
Customer Reviews	4.7 4.7 out of 5 stars (2,829)
Date First Available	January 31, 2012
Is Discontinued By Manufacturer	No
Item Weight	2.39 ounces
Item model number	CRMC-0015-CO
Manufacturer	CravenSpeed
Product Dimensions	0.63 x 0.63 x 4 inches

CravenSpeed Stubby Antenna Compatible with Mini Cooper 2001-2022 | 4 inches

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