gt 1030 in an optiplex 490

Solution
Do you mean a Precision 490? I'm drawing a blank on an Optiplex 490. if the MB has 6 expansion slots it's not an Opti.
Ok I'm guessing it's an Opti 390 which does exist. Is it the MT (Mini Tower), DT (Desktop), or SFF ( Small Form Factor)
Here are some builds. I would save up for a 11050Ti, the Dell manual doesn't list a 30W limit for any of the 390s.
http://www.userbenchmark.com/System/Dell-OptiPlex-390/1958
Also I saw an i5-2500k running in one of these. Throttlestop software mightget a few extra multipliers out of it. The 1030 would really be selling that system short.
Do you mean a Precision 490? I'm drawing a blank on an Optiplex 490. if the MB has 6 expansion slots it's not an Opti.
Ok I'm guessing it's an Opti 390 which does exist. Is it the MT (Mini Tower), DT (Desktop), or SFF ( Small Form Factor)
Here are some builds. I would save up for a 11050Ti, the Dell manual doesn't list a 30W limit for any of the 390s.
http://www.userbenchmark.com/System/Dell-OptiPlex-390/1958
Also I saw an i5-2500k running in one of these. Throttlestop software mightget a few extra multipliers out of it. The 1030 would really be selling that system short.
 
Solution
It's not about the motherboard but the fact that a 1050 ti is recommended to have a minimum 300W PSU, which is way more than what he have. Pushing these usually lower quality PSU used in brand name computers to or above the limit is absolutely not recommended and you risk frying your whole system or setting your house on fire.
 
The minimum PSU rating assumes a normal sized computer that has several drive bays (not just 1) , several HDDs, and several expansion slots with devices, and 4 memroy slots that this computer doesn't have. Dell under rates their PSUs because when you're selling computers to companies by the thousands efficiency adds up to a lot of money.
$20/Year X 1000 computers X 5 years=$100,000 So does reliability when they're all on service contract and extended warrantee. dell PSUs are probably some of the best in the business. certainly above average.

In the MT case Dell offers a 305W PSU, and a 255W EPA PSU. They both have the same output on all power rails. the 255w is 85% efficient, the 305w is 75%. So Dell gives the EPA a lower rating to show it's efficiency . Dell doesn't sell PSUs by the Watt like the aftermarket "Advertised" Watts you're used to. people have been running GTX750s on that PSU for years.
Actually if I were building that thing it would Have big PSU wired out the back as a power brick and an i5-2500k overclocked with Throttlestop software. But that's just me.
The 1050 draws 75W the 750 draws 65W The PSU has enough power and then some.